Laravel - Digging Deeper - Collections

5月 11 2020 Dev 1 小时讀完 (大概 6905 字)

前言

學習一個框架, Ray 的想法是, 在深入理解底層實作的原理之前, 應該先知道這個框架的 使用方法; 先學習怎麼使用這個前人造的輪子, 再學習怎麼樣造一個輪子。
所以本篇文章重點在於細讀官方文件, 並將內容理解後以 Q&A 的方式記錄下來, 加速學習以及查詢。

Introduction

Laravel Collections 中, 以下的 Example 的意思是？

Example

<?php
$collection = collect(['taylor', 'abigail', null])->map(function ($name) {
    return strtoupper($name);
})
->reject(function ($name) {
    return empty($name);
});

Answer

<?php
// 取得 collection instance 並將每個 entry 變成大寫
$collection = collect(['taylor', 'abigail', null])->map(function ($name) {
    return strtoupper($name);
})
// 移除 empty entry
->reject(function ($name) {
    return empty($name);
});

Extending Collections

Laravel Collections 中, 如果我要自定義一個 collection method, 在以下的 example 中, 該使用哪個 method?

Example

<?php
use Illuminate\Support\Collection;
use Illuminate\Support\Str;

Collection::這裡是？('toUpper', function () {
    return $this->map(function ($value) {
        return Str::upper($value);
    });
});

$collection = collect(['first', 'second']);

$upper = $collection->toUpper();

// ['FIRST', 'SECOND']

Answer

<?php
use Illuminate\Support\Collection;
use Illuminate\Support\Str;

Collection::macro('toUpper', function () {
    return $this->map(function ($value) {
        return Str::upper($value);
    });
});

$collection = collect(['first', 'second']);

$upper = $collection->toUpper();

// ['FIRST', 'SECOND']

Available Methods

Laravel Collections 中, 以下的 collection method 的輸出是？

Example
<?php
collect([1, 2, 3])->all();
Answer
// [1, 2, 3]

Laravel Collections 中, 以下的 collection example 中, $average 的值是？

Example

<?php
$average = collect([['foo' => 10], ['foo' => 10], ['foo' => 20], ['foo' => 40]])->avg('foo');

Answer
20

Laravel Collections 中, 以下的 collection example 中, $average 的值是？

Example

<?php
$average = collect([1, 1, 2, 4])->avg();

Answer
2

Laravel Collections 中, 以下的 collection example 中, $chunks 的值是？

Example

<?php
$collection = collect([1, 2, 3, 4, 5, 6, 7]);

$chunks = $collection->chunk(4);

$chunks->toArray();

Answer
<?php
// [[1, 2, 3, 4], [5, 6, 7]]

Laravel Collections 中, 以下的 collection example 中, $collapsed 的值是？

Example

<?php
$collection = collect([[1, 2, 3], [4, 5, 6], [7, 8, 9]]);

$collapsed = $collection->collapse();

$collapsed->all();

Answer
<?php
// [1, 2, 3, 4, 5, 6, 7, 8, 9]

Laravel Collections 中, 以下的 collection example 中, $combined 的值是？

Example

<?php
$collection = collect(['name', 'age']);

$combined = $collection->combine(['George', 29]);

$combined->all();

Answer

<?php
// ['name' => 'George', 'age' => 29]

Laravel Collections 中, 以下的 collection example 中, $collectionB 的值是？

Example

<?php
$collectionA = collect([1, 2, 3]);

$collectionB = $collectionA->collect();

$collectionB->all();

Answer
<?php
// [1, 2, 3]

以下的 Laravel example code 的意思是？

Example

<?php
$lazyCollection = LazyCollection::make(function () {
    yield 1;
    yield 2;
    yield 3;
});

$collection = $lazyCollection->collect();

get_class($collection);

// 'Illuminate\Support\Collection'

$collection->all();

// [1, 2, 3]

Answer
將 lazyCollection 轉成一般的 collection

Laravel Collections 中, 以下的 collection example 中, $concatenated 的值是？

Example

<?php
$collection = collect(['John Doe']);

$concatenated = $collection->concat(['Jane Doe'])->concat(['name' => 'Johnny Doe']);

$concatenated->all();

Answer

<?php
// ['John Doe', 'Jane Doe', 'Johnny Doe']

Laravel Collections 中, 以下的 example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'Desk', 'price' => 100]);

$collection->contains('Desk');

Answer:
true

Laravel Collections 中, 以下的 example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'Desk', 'price' => 100]);
$collection->contains('New York');

Answer:
false

Laravel Collections 中, 以下的 example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
]);

$collection->contains('product', 'Bookcase');

Answer:
false

以下的 Laravel Collections example 中, 邏輯是？

Example:

<?php
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
]);

$collection->contains('product', 'Bookcase');

// false

Answer:

<?php
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
]);

// 驗該 collection 中有無 'product' => 'Bookcase' 的 key / value 
$collection->contains('product', 'Bookcase');

// false

**以下的 Laravel Collections example 中, 如果我要判斷該 collection 中是否有大於 3 的 value, 該在 contains method 中帶入什麼參數？**

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$collection->contains(這裡是？);

// true

Answer:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$collection->contains(function ($value, $key) {
    return $value > 3;
});

// true

Laravel collection method contains() 是使用 loose comparison 還是 strict comparison?

loose comparison

**Laravel collection method contains() 跟 containsStrict() 差別是？**

contains(): loose comparison
containsStrict(): strict comparison

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$collection->count();

Answer:
4

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 2, 2, 3]);

$counted = $collection->countBy();

$counted->all();

Answer:

[1 => 1, 2 => 3, 3 => 1]

以下的 Laravel Collections example 中, 邏輯是？

Example:

<?php
$collection = collect(['alice@gmail.com', 'bob@yahoo.com', 'carlos@gmail.com']);

$counted = $collection->countBy(function ($email) {
    return substr(strrchr($email, "@"), 1);
});

$counted->all();

// ['gmail.com' => 2, 'yahoo.com' => 1]

Answer:

<?php
$collection = collect(['alice@gmail.com', 'bob@yahoo.com', 'carlos@gmail.com']);

// strrchr 取得 "@ 最後一次出現的位置" 到 "最末" 字串, 即 @yahoo.com, @carlos@gmail.com
// substr 取得位置 1 到最末, 即 yahoo.com, carlos@gmail
$counted = $collection->countBy(function ($email) {
    return substr(strrchr($email, "@"), 1);
});

$counted->all();

// ['gmail.com' => 2, 'yahoo.com' => 1]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2]);

$matrix = $collection->crossJoin(['a', 'b']);

$matrix->all();

Answer:

<?php
/*
    [
        [1, 'a'],
        [1, 'b'],
        [2, 'a'],
        [2, 'b'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2]);

$matrix = $collection->crossJoin(['a', 'b'], ['I', 'II']);

$matrix->all();

Example:

<?php
/*
    [
        [1, 'a', 'I'],
        [1, 'a', 'II'],
        [1, 'b', 'I'],
        [1, 'b', 'II'],
        [2, 'a', 'I'],
        [2, 'a', 'II'],
        [2, 'b', 'I'],
        [2, 'b', 'II'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['John Doe', 'Jane Doe']);

$collection->dd();

Answer:

<?php
/*
    Collection {
        #items: array:2 [
            0 => "John Doe"
            1 => "Jane Doe"
        ]
    }
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$diff = $collection->diff([2, 4, 6, 8]);

$diff->all();

Answer:
<?php
// [1, 3, 5]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    'color' => 'orange',
    'type' => 'fruit',
    'remain' => 6
]);

$diff = $collection->diffAssoc([
    'color' => 'yellow',
    'type' => 'fruit',
    'remain' => 3,
    'used' => 6,
]);

$diff->all();

Answer:

<?php
// ['color' => 'orange', 'remain' => 6]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    'one' => 10,
    'two' => 20,
    'three' => 30,
    'four' => 40,
    'five' => 50,
]);

$diff = $collection->diffKeys([
    'two' => 2,
    'four' => 4,
    'six' => 6,
    'eight' => 8,
]);

$diff->all();

Answer:

<?php
// ['one' => 10, 'three' => 30, 'five' => 50]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['John Doe', 'Jane Doe']);

$collection->dump();

Answer:

<?php
/*
    Collection {
        #items: array:2 [
            0 => "John Doe"
            1 => "Jane Doe"
        ]
    }
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['a', 'b', 'a', 'c', 'b']);

$collection->duplicates();

Answer:
<?php
// [2 => 'a', 4 => 'b']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$employees = collect([
    ['email' => 'abigail@example.com', 'position' => 'Developer'],
    ['email' => 'james@example.com', 'position' => 'Designer'],
    ['email' => 'victoria@example.com', 'position' => 'Developer'],
])

$employees->duplicates('position');

Answer:
<?php
// [2 => 'Developer']

**以下的 Laravel Collections method duplicates 跟 duplicatesStrict 差別在於？？**

loose comparison 與 strict comparison

以下的 Laravel Collections method 中, foeach 相當於哪個 collection method?？

collection.each

**以下的 Laravel Collections method each 中, 在以下的 example, 如果我要打斷 iteration, 該怎麼做？**

Example:

<?php
$collection->each(function ($item, $key) {
    if (/* some condition */) {
        // 這裡要 return?
    }
});

Answer:

<?php
$collection->each(function ($item, $key) {
    if (/* some condition */) {
        return false;
    }
});

以下的 Laravel example code 的意思是？

Example:

<?php
$collection = collect([['John Doe', 35], ['Jane Doe', 33]]);

$collection->eachSpread(function ($name, $age) {
    //
});

Answer:
使用 eachSpread iterate 每一個 nested item, 如果裡頭的動作是 echo $name, 輸出為 John Doe, Jane Doe

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
collect([1, 2, 3, 4])->every(function ($value, $key) {
    return $value > 2;
});

Answer:
<?php
// false

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([]);

$collection->every(function ($value, $key) {
    return $value > 2;
});

Answer:
// true

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['product_id' => 1, 'price' => 100, 'discount' => false]);

$filtered = $collection->except(['price', 'discount']);

$filtered->all();

Answer:
<?php
// ['product_id' => 1]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$filtered = $collection->filter(function ($value, $key) {
    return $value > 2;
});

$filtered->all();

Answer:
<?php
// [3, 4]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, null, false, '', 0, []]);

$collection->filter()->all();

Answer:
<?php
// [1, 2, 3]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
collect([1, 2, 3, 4])->first(function ($value, $key) {
    return $value > 2;
});

Answer:
<?php
// 3

以下的 Laravel Collections example 中, 輸出是？

Example:
<?php
collect([1, 2, 3, 4])->first();
Answer:
<?php
// 1

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'Regena', 'age' => null],
    ['name' => 'Linda', 'age' => 14],
    ['name' => 'Diego', 'age' => 23],
    ['name' => 'Linda', 'age' => 84],
]);

$collection->firstWhere('name', 'Linda');

Answer:

<?php
// ['name' => 'Linda', 'age' => 14]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'Regena', 'age' => null],
    ['name' => 'Linda', 'age' => 14],
    ['name' => 'Diego', 'age' => 23],
    ['name' => 'Linda', 'age' => 84],
]);

$collection->firstWhere('age', '>=', 18);

Answer:

<?php
// ['name' => 'Diego', 'age' => 23]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'Regena', 'age' => null],
    ['name' => 'Linda', 'age' => 14],
    ['name' => 'Diego', 'age' => 23],
    ['name' => 'Linda', 'age' => 84],
]);

$collection->firstWhere('age');

Answer:

<?php
// ['name' => 'Linda', 'age' => 14]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'Sally'],
    ['school' => 'Arkansas'],
    ['age' => 28]
]);

$flattened = $collection->flatMap(function ($values) {
    return array_map('strtoupper', $values);
});

$flattened->all();

Answer:

<?php
// ['name' => 'SALLY', 'school' => 'ARKANSAS', 'age' => '28'];

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'taylor', 'languages' => ['php', 'javascript']]);

$flattened = $collection->flatten();

$flattened->all();

Answer:

<?php
// ['taylor', 'php', 'javascript'];

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    'Apple' => [
        ['name' => 'iPhone 6S', 'brand' => 'Apple'],
    ],
    'Samsung' => [
        ['name' => 'Galaxy S7', 'brand' => 'Samsung']
    ],
]);

$products = $collection->flatten(1);

$products->values()->all();

Answer:

<?php
/*
    [
        ['name' => 'iPhone 6S', 'brand' => 'Apple'],
        ['name' => 'Galaxy S7', 'brand' => 'Samsung'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    'Apple' => [
        ['name' => 'iPhone 6S', 'brand' => 'Apple'],
    ],
    'Samsung' => [
        ['name' => 'Galaxy S7', 'brand' => 'Samsung']
    ],
]);

$products = $collection->flatten();

$products->values()->all();

Answer:

<?php
// ['iPhone 6S', 'Apple', 'Galaxy S7', 'Samsung']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);

$flipped = $collection->flip();

$flipped->all();

Answer:

<?php
// ['taylor' => 'name', 'laravel' => 'framework']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);

$collection->forget('name');

$collection->all();

Answer:
<?php
// ['framework' => 'laravel']

**Laravel collection method reject 跟 forget 差別是？**

reject 會 return 一個新的 collection, forget 修改原本的 collection

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9]);

$chunk = $collection->forPage(2, 3);

$chunk->all();

Answer:
<?php
// [4, 5, 6]

以下的 Laravel Collections example 中, forPage method 的 argument 代表的意思是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9]);

$chunk = $collection->forPage(2, 3);

$chunk->all();

// [4, 5, 6]

Answer:

<?php
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9]);

// 2 代表第二頁的內容, 3 代表每頁顯示 3 筆資料
$chunk = $collection->forPage(2, 3);

$chunk->all();

// [4, 5, 6]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);

$value = $collection->get('name');

Answer:
<?php
// taylor

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);

$value = $collection->get('hello');

Answer:
<?php
// null

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);

$value = $collection->get('foo', 'default-value');

Answer:
<?php
// default-value

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'taylor', 'framework' => 'laravel']);

$collection->get('email', function () {
    return 'default-value';
});

Answer:
<?php
// default-value

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['email' => 'ray@gmail.com', 'name' => 'taylor', 'framework' => 'laravel']);

$collection->get('email', function () {
    return 'default-value';
});

Answer:
<?php
// ['email' => 'ray@gmail.com']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['account_id' => 'account-x10', 'product' => 'Chair'],
    ['account_id' => 'account-x10', 'product' => 'Bookcase'],
    ['account_id' => 'account-x11', 'product' => 'Desk'],
]);

$grouped = $collection->groupBy('account_id');

$grouped->toArray();

Answer:

<?php
/*
    [
        'account-x10' => [
            ['account_id' => 'account-x10', 'product' => 'Chair'],
            ['account_id' => 'account-x10', 'product' => 'Bookcase'],
        ],
        'account-x11' => [
            ['account_id' => 'account-x11', 'product' => 'Desk'],
        ],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['account_id' => 'account-x10', 'product' => 'Chair'],
    ['account_id' => 'account-x10', 'product' => 'Bookcase'],
    ['account_id' => 'account-x11', 'product' => 'Desk'],
]);

$grouped = $collection->groupBy(function ($item, $key) {
    return substr($item['account_id'], -3);
});

$grouped->toArray();

Answer:

<?php
/*
    [
        'x10' => [
            ['account_id' => 'account-x10', 'product' => 'Chair'],
            ['account_id' => 'account-x10', 'product' => 'Bookcase'],
        ],
        'x11' => [
            ['account_id' => 'account-x11', 'product' => 'Desk'],
        ],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$data = new Collection([
    10 => ['user' => 1, 'skill' => 1, 'roles' => ['Role_1', 'Role_3']],
    20 => ['user' => 2, 'skill' => 1, 'roles' => ['Role_1', 'Role_2']],
    30 => ['user' => 3, 'skill' => 2, 'roles' => ['Role_1']],
    40 => ['user' => 4, 'skill' => 2, 'roles' => ['Role_2']],
]);

$result = $data->groupBy([
    'skill',
    function ($item) {
        return $item['roles'];
    },
], $preserveKeys = true);

Answer:

<?php

/*
[
    1 => [
        'Role_1' => [
            10 => ['user' => 1, 'skill' => 1, 'roles' => ['Role_1', 'Role_3']],
            20 => ['user' => 2, 'skill' => 1, 'roles' => ['Role_1', 'Role_2']],
        ],
        'Role_2' => [
            20 => ['user' => 2, 'skill' => 1, 'roles' => ['Role_1', 'Role_2']],
        ],
        'Role_3' => [
            10 => ['user' => 1, 'skill' => 1, 'roles' => ['Role_1', 'Role_3']],
        ],
    ],
    2 => [
        'Role_1' => [
            30 => ['user' => 3, 'skill' => 2, 'roles' => ['Role_1']],
        ],
        'Role_2' => [
            40 => ['user' => 4, 'skill' => 2, 'roles' => ['Role_2']],
        ],
    ],
];
*/

**Laravel collection method contains 與 has 的差異是？**

contains() 帶入一組 array 的 key/value, 或單組 key
has() 帶入多個 key, 以 array 的形式

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['account_id' => 1, 'product' => 'Desk', 'amount' => 5]);

$collection->has('product');
// 輸出是？

$collection->has(['product', 'amount']);
// 輸出是？

$collection->has(['amount', 'price']);
// 輸出是？

Answer:
<?php
// true
// true
// false

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['account_id' => 1, 'product' => 'Desk'],
    ['account_id' => 2, 'product' => 'Chair'],
]);

$collection->implode('product', ', ');

Answer:
<?php
// Desk, Chair

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
collect([1, 2, 3, 4, 5])->implode('-');

Answer:
<?php
// '1-2-3-4-5'

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['Desk', 'Sofa', 'Chair']);

$intersect = $collection->intersect(['Desk', 'Chair', 'Bookcase']);

$intersect->all();

Answer:
<?php
// [0 => 'Desk', 2 => 'Chair']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    'serial' => 'UX301', 'type' => 'screen', 'year' => 2009
]);

$intersect = $collection->intersectByKeys([
    'reference' => 'UX404', 'type' => 'tab', 'year' => 2011
]);

$intersect->all();

Answer:

<?php
// ['type' => 'screen', 'year' => 2009]

以下的 Laravel Collections example 中, 輸出是？

Example:
<?php
collect([])->isEmpty();
Answer:
<?php
// true

以下的 Laravel example code 的意思是？

Example:
<?php
collect([])->isNotEmpty();
Answer:
false
判斷該 collection 是否為 empty

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
collect(['a', 'b', 'c'])->join(', ');

Answer:
<?php
// 'a, b, c'

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
collect(['a', 'b', 'c'])->join(', ', ', and ');

Answer:
<?php
// 'a, b, and c'

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
collect(['a', 'b'])->join(', ', ' and ');

Answer:
<?php
// 'a and b'

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
collect(['a'])->join(', ', ' and ');

Answer:
<?php
// 'a'

以下的 Laravel Collections example 中, 輸出是？

Example:
<?php
collect([])->join(', ', ' and ');
Answer:
<?php
// ''

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product_id' => 'prod-100', 'name' => 'Desk'],
    ['product_id' => 'prod-200', 'name' => 'Chair'],
]);

$keyed = $collection->keyBy('product_id');

$keyed->all();

Answer:

<?php
/*
    [
        'prod-100' => ['product_id' => 'prod-100', 'name' => 'Desk'],
        'prod-200' => ['product_id' => 'prod-200', 'name' => 'Chair'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product_id' => 'prod-100', 'name' => 'Desk'],
    ['product_id' => 'prod-100', 'name' => 'Chair'],
]);

$keyed = $collection->keyBy('product_id');

$keyed->all();

Answer:

<?php
/*
    [
        'prod-100' => ['product_id' => 'prod-200', 'name' => 'Chair'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product_id' => 'prod-100', 'name' => 'Desk'],
    ['product_id' => 'prod-200', 'name' => 'Chair'],
]);

$keyed = $collection->keyBy(function ($item) {
    return strtoupper($item['product_id']);
});

$keyed->all();

Answer:

<?php
/*
    [
        'PROD-100' => ['product_id' => 'prod-100', 'name' => 'Desk'],
        'PROD-200' => ['product_id' => 'prod-200', 'name' => 'Chair'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    'prod-100' => ['product_id' => 'prod-100', 'name' => 'Desk'],
    'prod-200' => ['product_id' => 'prod-200', 'name' => 'Chair'],
]);

$keys = $collection->keys();

$keys->all();

Answer:
<?php
// ['prod-100', 'prod-200']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
collect([1, 2, 3, 4])->last(function ($value, $key) {
    return $value < 3;
});

Answer:
<?php
// 2

以下的 Laravel Collections example 中, 輸出是？

Example:
<?php
collect([1, 2, 3, 4])->last();
Answer:
<?php
// 4

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$multiplied = $collection->map(function ($item, $key) {
    return $item * 2;
});

$multiplied->all();

Answer:
<?php
// [2, 4, 6, 8, 10]

**Laravel collection method map() 與 transform(), 差別在於？**

map 產生新的 collection, transform 修改現有的 collection

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
class Currency
{
    function __construct(string $code)
    {
        $this->code = $code;
    }
}

$collection = collect(['USD', 'EUR', 'GBP']);

$currencies = $collection->mapInto(Currency::class);

$currencies->all();

Answer:

<?php
// [Currency('USD'), Currency('EUR'), Currency('GBP')]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);

$chunks = $collection->chunk(2);

$sequence = $chunks->mapSpread(function ($even, $odd) {
    return $even + $odd;
});

$sequence->all();

Answer:
<?php
// [1, 5, 9, 13, 17]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    [
        'name' => 'John Doe',
        'department' => 'Sales',
    ],
    [
        'name' => 'Jane Doe',
        'department' => 'Sales',
    ],
    [
        'name' => 'Johnny Doe',
        'department' => 'Marketing',
    ]
]);

$grouped = $collection->mapToGroups(function ($item, $key) {
    return [$item['department'] => $item['name']];
});

$grouped->toArray();

Answer:

<?php
/*
    [
        'Sales' => ['John Doe', 'Jane Doe'],
        'Marketing' => ['Johnny Doe'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    [
        'name' => 'John Doe',
        'department' => 'Sales',
    ],
    [
        'name' => 'Jane Doe',
        'department' => 'Sales',
    ],
    [
        'name' => 'Johnny Doe',
        'department' => 'Marketing',
    ]
]);

$grouped = $collection->mapToGroups(function ($item, $key) {
    return [$item['department'] => $item['name']];
});
$grouped->get('Sales')->all();

Answer:
<?php
// ['John Doe', 'Jane Doe']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    [
        'name' => 'John',
        'department' => 'Sales',
        'email' => 'john@example.com'
    ],
    [
        'name' => 'Jane',
        'department' => 'Marketing',
        'email' => 'jane@example.com'
    ]
]);

$keyed = $collection->mapWithKeys(function ($item) {
    return [$item['email'] => $item['name']];
});

$keyed->all();

Answer:

<?php
/*
    [
        'john@example.com' => 'John',
        'jane@example.com' => 'Jane',
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$max = collect([['foo' => 10], ['foo' => 20]])->max('foo');
// $max 輸出是？

$max = collect([1, 2, 3, 4, 5])->max();
// $max 輸出是？

Answer:
<?php
// 20

// 5

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$median = collect([['foo' => 10], ['foo' => 10], ['foo' => 20], ['foo' => 40]])->median('foo');
// $median 輸出是？

$median = collect([1, 1, 2, 4])->median();
// $median 輸出是？

Answer:
<?php
// 15

// 1.5

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['product_id' => 1, 'price' => 100]);

$merged = $collection->merge(['price' => 200, 'discount' => false]);

$merged->all();

Answer:

<?php
// ['product_id' => 1, 'price' => 200, 'discount' => false]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['Desk', 'Chair']);

$merged = $collection->merge(['Bookcase', 'Door']);

$merged->all();

Answer:

<?php
// ['Desk', 'Chair', 'Bookcase', 'Door']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['product_id' => 1, 'price' => 100]);

$merged = $collection->mergeRecursive(['product_id' => 2, 'price' => 200, 'discount' => false]);

$merged->all();

Answer:

<?php
// ['product_id' => [1, 2], 'price' => [100, 200], 'discount' => false]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$min = collect([['foo' => 10], ['foo' => 20]])->min('foo');
// $min 輸出是？

$min = collect([1, 2, 3, 4, 5])->min();
// $min 輸出是？

Answer:
<?php
// 10

// 1

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$mode = collect([['foo' => 10], ['foo' => 10], ['foo' => 20], ['foo' => 40]])->mode('foo');
// $mode 輸出是？

$mode = collect([1, 1, 2, 4])->mode();
// $mode 輸出是？

Answer:
<?php
// [10]

// [1]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['a', 'b', 'c', 'd', 'e', 'f']);

$collection->nth(4);

Answer:
<?php
// ['a', 'e']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['a', 'b', 'c', 'd', 'e', 'f']);

$collection->nth(4, 1);

Answer:
<?php
// ['b', 'f']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['product_id' => 1, 'name' => 'Desk', 'price' => 100, 'discount' => false]);

$filtered = $collection->only(['product_id', 'name']);

$filtered->all();

Answer:

<?php
// ['product_id' => 1, 'name' => 'Desk']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['A', 'B', 'C']);

$filtered = $collection->pad(5, 0);

$filtered->all();

// $filtered 輸出是？

$filtered = $collection->pad(-5, 0);

$filtered->all();

// $filtered 輸出是？

Answer:

<?php
// ['A', 'B', 'C', 0, 0]

// [0, 0, 'A', 'B', 'C']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5, 6]);

list($underThree, $equalOrAboveThree) = $collection->partition(function ($i) {
    return $i < 3;
});

$underThree->all();
// $underThree 輸出是？

$equalOrAboveThree->all();
// $equalOrAboveThree 輸出是？

Answer:
<?php
// [1, 2]

// [3, 4, 5, 6]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3]);

$piped = $collection->pipe(function ($collection) {
    return $collection->sum();
});

Answer:
<?php
// 6

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product_id' => 'prod-100', 'name' => 'Desk'],
    ['product_id' => 'prod-200', 'name' => 'Chair'],
]);

$plucked = $collection->pluck('name');

$plucked->all();

Answer:
<?php
// ['Desk', 'Chair']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product_id' => 'prod-100', 'name' => 'Desk'],
    ['product_id' => 'prod-200', 'name' => 'Chair'],
]);

$plucked = $collection->pluck('name', 'product_id');

$plucked->all();

Answer:

<?php
// ['prod-100' => 'Desk', 'prod-200' => 'Chair']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['brand' => 'Tesla',  'color' => 'red'],
    ['brand' => 'Pagani', 'color' => 'white'],
    ['brand' => 'Tesla',  'color' => 'black'],
    ['brand' => 'Pagani', 'color' => 'orange'],
]);

$plucked = $collection->pluck('color', 'brand');

$plucked->all();

Answer:

<?php
// ['Tesla' => 'black', 'Pagani' => 'orange']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$collection->pop();
// 這裡的輸出是？

$collection->all();
// 這裡的輸出是？

Answer:
<?php
// 5

// [1, 2, 3, 4]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$collection->prepend(0);

$collection->all();

Answer:
<?php
// [0, 1, 2, 3, 4, 5]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['one' => 1, 'two' => 2]);

$collection->prepend(0, 'zero');

$collection->all();

Answer:

<?php
// ['zero' => 0, 'one' => 1, 'two' => 2]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['product_id' => 'prod-100', 'name' => 'Desk']);

$collection->pull('name');
// 這裡的輸出是？

$collection->all();
// 這裡的輸出是？

Answer:

<?php
// 'Desk'

// ['product_id' => 'prod-100']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$collection->push(5);

$collection->all();

Answer:
<?php
// [1, 2, 3, 4, 5]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['product_id' => 1, 'name' => 'Desk']);

$collection->put('price', 100);

$collection->all();

Answer:

<?php
// ['product_id' => 1, 'name' => 'Desk', 'price' => 100]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$collection->random();

Answer:
<?php
// 4 - (retrieved randomly)

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$random = $collection->random(3);

$random->all();

Answer:

<?php
// [2, 4, 5] - (retrieved randomly)

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3]);

$total = $collection->reduce(function ($carry, $item) {
    return $carry + $item;
});

Answer:
<?php
// 6

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3]);

$collection->reduce(function ($carry, $item) {
    return $carry + $item;
}, 4);

Answer:
<?php
// 10

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$filtered = $collection->reject(function ($value, $key) {
    return $value > 2;
});

$filtered->all();

Answer:
<?php
// [1, 2]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['Taylor', 'Abigail', 'James']);

$replaced = $collection->replace([1 => 'Victoria', 3 => 'Finn']);

$replaced->all();

Answer:

<?php
// ['Taylor', 'Victoria', 'James', 'Finn']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['Taylor', 'Abigail', ['James', 'Victoria', 'Finn']]);

$replaced = $collection->replaceRecursive(['Charlie', 2 => [1 => 'King']]);

$replaced->all();

Answer:

<?php
// ['Charlie', 'Abigail', ['James', 'King', 'Finn']]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['a', 'b', 'c', 'd', 'e']);

$reversed = $collection->reverse();

$reversed->all();

Answer:

<?php
/*
    [
        4 => 'e',
        3 => 'd',
        2 => 'c',
        1 => 'b',
        0 => 'a',
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([2, 4, 6, 8]);

$collection->search(4);

Answer:
<?php
// 1

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([2, 4, 6, 8]);

$collection->search('4', true);

Answer:
<?php
// false

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([2, 4, 6, 8]);

$collection->search(function ($item, $key) {
    return $item > 5;
});

Answer:
<?php
// 2

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$collection->shift();
// 這裡輸出是？

$collection->all();
// 這裡輸出是？

Answer:
<?php
// 1

// [2, 3, 4, 5]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$shuffled = $collection->shuffle();

$shuffled->all();

Answer:

<?php
// [3, 2, 5, 1, 4] - (generated randomly)

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);

$collection = $collection->skip(4);

$collection->all();

Answer:
<?php
// [5, 6, 7, 8, 9, 10]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$subset = $collection->skipUntil(function ($item) {
    return $item >= 3;
});

$subset->all();

Answer:
<?php
// [3, 4]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);

$collection = $collection->skip(4);

$collection->all();

Answer:
<?php
// [5, 6, 7, 8, 9, 10]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$subset = $collection->skipUntil(3);

$subset->all();

Answer:
<?php
// [3, 4]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$subset = $collection->skipWhile(function ($item) {
    return $item <= 3;
});

$subset->all();

Answer:
<?php
// [4]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);

$slice = $collection->slice(4);

$slice->all();

Answer:
<?php
// [5, 6, 7, 8, 9, 10]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);

$slice = $collection->slice(4, 2);

$slice->all();

Answer:
<?php
// [5, 6]

Laravel Collections method `some()` 是哪一個 method 的 alias？

contains()

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([5, 3, 1, 2, 4]);

$sorted = $collection->sort();

$sorted->values()->all();

Answer:
<?php
// [1, 2, 3, 4, 5]

Laravel Collections method `sort()` 是否會保留原本的 index？

會的

Laravel Collections method `slice()` 是否會保留原本的 index？

會的

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'Desk', 'price' => 200],
    ['name' => 'Chair', 'price' => 100],
    ['name' => 'Bookcase', 'price' => 150],
]);

$sorted = $collection->sortBy('price');

$sorted->values()->all();

Answer:

<?php

/*
    [
        ['name' => 'Chair', 'price' => 100],
        ['name' => 'Bookcase', 'price' => 150],
        ['name' => 'Desk', 'price' => 200],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'Desk', 'colors' => ['Black', 'Mahogany']],
    ['name' => 'Chair', 'colors' => ['Black']],
    ['name' => 'Bookcase', 'colors' => ['Red', 'Beige', 'Brown']],
]);

$sorted = $collection->sortBy(function ($product, $key) {
    return count($product['colors']);
});

$sorted->values()->all();

Answer:

<?php

/*
    [
        ['name' => 'Chair', 'colors' => ['Black']],
        ['name' => 'Desk', 'colors' => ['Black', 'Mahogany']],
        ['name' => 'Bookcase', 'colors' => ['Red', 'Beige', 'Brown']],
    ]
*/

Laravel Collections method 中, `sortBy` 跟 `sortByDesc` 差別在哪？

反方向

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([5, 3, 1, 2, 4]);

$sorted = $collection->sortDesc();

$sorted->values()->all();

Answer:
<?php

// [5, 4, 3, 2, 1]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    'id' => 22345,
    'first' => 'John',
    'last' => 'Doe',
]);

$sorted = $collection->sortKeys();

$sorted->all();

Answer:

<?php

/*
    [
        'first' => 'John',
        'id' => 22345,
        'last' => 'Doe',
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    'id' => 22345,
    'first' => 'John',
    'last' => 'Doe',
]);

$sorted = $collection->sortKeysDesc();

$sorted->all();

Answer:

<?php

/*
    [
        'last' => 'Doe',
        'id' => 22345,
        'first' => 'John',
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$chunk = $collection->splice(2);

$chunk->all();

// 這裡輸出是？

$collection->all();
// 這裡輸出是？

Answer:
<?php
// [3, 4, 5]

// [1, 2]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$chunk = $collection->splice(2, 1);

$chunk->all();
// 這裡輸出是？

$collection->all();
// 這裡輸出是？

Answer:
<?php

// [3]

// [1, 2, 4, 5]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$chunk = $collection->splice(2, 1, [10, 11]);

$chunk->all();
// 這裡輸出是？

$collection->all();
// 這裡輸出是？

Answer:
<?php

// [3]

// [1, 2, 10, 11, 4, 5]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$groups = $collection->split(3);

$groups->toArray();

Answer:
<?php

// [[1, 2], [3, 4], [5]]

以下的 Laravel Collections example 中, 輸出是？

Example:
<?php
collect([1, 2, 3, 4, 5])->sum();
Answer:
<?php

// 15

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'JavaScript: The Good Parts', 'pages' => 176],
    ['name' => 'JavaScript: The Definitive Guide', 'pages' => 1096],
]);

$collection->sum('pages');

Answer:
<?php

// 1272

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'Chair', 'colors' => ['Black']],
    ['name' => 'Desk', 'colors' => ['Black', 'Mahogany']],
    ['name' => 'Bookcase', 'colors' => ['Red', 'Beige', 'Brown']],
]);

$collection->sum(function ($product) {
    return count($product['colors']);
});

Answer:
<?php

// 6

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([0, 1, 2, 3, 4, 5]);

$chunk = $collection->take(3);

$chunk->all();

Answer:
<?php

// [0, 1, 2]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([0, 1, 2, 3, 4, 5]);

$chunk = $collection->take(-2);

$chunk->all();

Answer:
<?php

// [4, 5]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$subset = $collection->takeUntil(function ($item) {
    return $item >= 3;
});

$subset->all();

Answer:
<?php

// [1, 2]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$subset = $collection->takeUntil(3);

$subset->all();

Answer:
<?php
// [1, 2]
3 表示 value, 非 index

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4]);

$subset = $collection->takeWhile(function ($item) {
    return $item < 3;
});

$subset->all();

Answer:
<?php

// [1, 2]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
collect([2, 4, 3, 1, 5])
    ->sort()
    ->tap(function ($collection) {
        Log::debug('Values after sorting', $collection->values()->toArray());
    })
    ->shift();

Answer:
<?php

// 1

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = Collection::times(10, function ($number) {
    return $number * 9;
});

$collection->all();

Answer:

<?php

// [9, 18, 27, 36, 45, 54, 63, 72, 81, 90]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$categories = Collection::times(3, function ($number) {
    return factory(Category::class)->create(['name' => "Category No. $number"]);
});

$categories->all();

Answer:

<?php

/*
    [
        ['id' => 1, 'name' => 'Category No. 1'],
        ['id' => 2, 'name' => 'Category No. 2'],
        ['id' => 3, 'name' => 'Category No. 3'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'Desk', 'price' => 200]);

$collection->toArray();

Answer:

<?php

/*
    [
        ['name' => 'Desk', 'price' => 200],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['name' => 'Desk', 'price' => 200]);

$collection->toJson();

Answer:
<?php

// '{"name":"Desk", "price":200}'

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3, 4, 5]);

$collection->transform(function ($item, $key) {
    return $item * 2;
});

$collection->all();

Answer:
<?php

// [2, 4, 6, 8, 10]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1 => ['a'], 2 => ['b']]);

$union = $collection->union([3 => ['c'], 1 => ['b']]);

$union->all();

Answer:

<?php

// [1 => ['a'], 2 => ['b'], 3 => ['c']]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 1, 2, 2, 3, 4, 2]);

$unique = $collection->unique();

$unique->values()->all();

Answer:
<?php

// [1, 2, 3, 4]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'iPhone 6', 'brand' => 'Apple', 'type' => 'phone'],
    ['name' => 'iPhone 5', 'brand' => 'Apple', 'type' => 'phone'],
    ['name' => 'Apple Watch', 'brand' => 'Apple', 'type' => 'watch'],
    ['name' => 'Galaxy S6', 'brand' => 'Samsung', 'type' => 'phone'],
    ['name' => 'Galaxy Gear', 'brand' => 'Samsung', 'type' => 'watch'],
]);

$unique = $collection->unique('brand');

$unique->values()->all();

Answer:

<?php

/*
    [
        ['name' => 'iPhone 6', 'brand' => 'Apple', 'type' => 'phone'],
        ['name' => 'Galaxy S6', 'brand' => 'Samsung', 'type' => 'phone'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'iPhone 6', 'brand' => 'Apple', 'type' => 'phone'],
    ['name' => 'iPhone 5', 'brand' => 'Apple', 'type' => 'phone'],
    ['name' => 'Apple Watch', 'brand' => 'Apple', 'type' => 'watch'],
    ['name' => 'Galaxy S6', 'brand' => 'Samsung', 'type' => 'phone'],
    ['name' => 'Galaxy Gear', 'brand' => 'Samsung', 'type' => 'watch'],
]);

$unique = $collection->unique(function ($item) {
    return $item['brand'].$item['type'];
});

$unique->values()->all();

Example:

<?php

/*
    [
        ['name' => 'iPhone 6', 'brand' => 'Apple', 'type' => 'phone'],
        ['name' => 'Apple Watch', 'brand' => 'Apple', 'type' => 'watch'],
        ['name' => 'Galaxy S6', 'brand' => 'Samsung', 'type' => 'phone'],
        ['name' => 'Galaxy Gear', 'brand' => 'Samsung', 'type' => 'watch'],
    ]
*/

Laravel Collections method `unique` 是 loose comparisons or strict comparison?

loose comparison

如果要使用 Laravel Collections method `unique` strict comparison 的話, 該使用哪個 method?

uniqueStrict()

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3]);

$collection->unless(true, function ($collection) {
    return $collection->push(4);
});

$collection->unless(false, function ($collection) {
    return $collection->push(5);
});

$collection->all();

Answer:
<?php

// [1, 2, 3, 5]

Laravel Collections method 中, `unlessEmpty` 是哪個 method 的 alias?

whenNotEmpty()

Laravel Collections method 中, `unlessNotEmpty` 是哪個 method 的 alias?

whenEmpty()

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
Collection::unwrap(collect('John Doe'));
// 這裡輸出是？

Collection::unwrap(['John Doe']);
// 這裡輸出是？

Collection::unwrap('John Doe');
// 這裡輸出是？

Answer:

<?php
// 如果 argument 是 array, 輸出 array, 否則則輸出 argument 本身

// ['John Doe']

// ['John Doe']

// 'John Doe'

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    10 => ['product' => 'Desk', 'price' => 200],
    11 => ['product' => 'Desk', 'price' => 200]
]);

$values = $collection->values();

$values->all();

Answer:

<?php
// 會重置 key

/*
    [
        0 => ['product' => 'Desk', 'price' => 200],
        1 => ['product' => 'Desk', 'price' => 200],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([1, 2, 3]);

$collection->when(true, function ($collection) {
    return $collection->push(4);
});

$collection->when(false, function ($collection) {
    return $collection->push(5);
});

$collection->all();

Answer:

<?php
// 恰恰與 unless 相反

// [1, 2, 3, 4]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['michael', 'tom']);

$collection->whenEmpty(function ($collection) {
    return $collection->push('adam');
});

$collection->all();

// ['michael', 'tom']

Answer:

<?php
當 $collection 為 empty 時, 執行 closure 內的邏輯
// ['michael', 'tom']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect();

$collection->whenEmpty(function ($collection) {
    return $collection->push('adam');
});

$collection->all();

Answer:
<?php

// ['adam']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['michael', 'tom']);

$collection->whenEmpty(function ($collection) {
    return $collection->push('adam');
}, function ($collection) {
    return $collection->push('taylor');
});

$collection->all();

Answer:
<?php

// ['michael', 'tom', 'taylor']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['michael', 'tom']);

$collection->whenNotEmpty(function ($collection) {
    return $collection->push('adam');
});

$collection->all();

Answer:
<?php

// ['michael', 'tom', 'adam']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect();

$collection->whenNotEmpty(function ($collection) {
    return $collection->push('adam');
});

$collection->all();

Answer:
<?php

// []

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect();

$collection->whenNotEmpty(function ($collection) {
    return $collection->push('adam');
}, function ($collection) {
    return $collection->push('taylor');
});

$collection->all();

Answer:
<?php

// ['taylor']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
    ['product' => 'Bookcase', 'price' => 150],
    ['product' => 'Door', 'price' => 100],
]);

$filtered = $collection->where('price', 100);

$filtered->all();

Answer:

<?php
/*
    [
        ['product' => 'Chair', 'price' => 100],
        ['product' => 'Door', 'price' => 100],
    ]
*/

Laravel collection method `where()` 預設是 loose comparison, 如果要讓它是 strict comparison, 該使用哪個 method?

whereStrict

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 80],
    ['product' => 'Bookcase', 'price' => 150],
    ['product' => 'Pencil', 'price' => 30],
    ['product' => 'Door', 'price' => 100],
]);

$filtered = $collection->whereBetween('price', [100, 200]);

$filtered->all();

Answer:

<?php

/*
    [
        ['product' => 'Desk', 'price' => 200],
        ['product' => 'Bookcase', 'price' => 150],
        ['product' => 'Door', 'price' => 100],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
    ['product' => 'Bookcase', 'price' => 150],
    ['product' => 'Door', 'price' => 100],
]);

$filtered = $collection->whereIn('price', [150, 200]);

$filtered->all();

Answer:

<?php

/*
    [
        ['product' => 'Desk', 'price' => 200],
        ['product' => 'Bookcase', 'price' => 150],
    ]
*/

Laravel collection method `whereIn()` 預設是 loose comparison, 如果要讓它是 strict comparison, 該使用哪個 method?

whereInStrict

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
use App\User;
use App\Post;

$collection = collect([
    new User,
    new User,
    new Post,
]);

$filtered = $collection->whereInstanceOf(User::class);

$filtered->all();

Answer:
<?php

// [App\User, App\User]

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 80],
    ['product' => 'Bookcase', 'price' => 150],
    ['product' => 'Pencil', 'price' => 30],
    ['product' => 'Door', 'price' => 100],
]);

$filtered = $collection->whereNotBetween('price', [100, 200]);

$filtered->all();

Answer:

<?php

/*
    [
        ['product' => 'Chair', 'price' => 80],
        ['product' => 'Pencil', 'price' => 30],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['product' => 'Desk', 'price' => 200],
    ['product' => 'Chair', 'price' => 100],
    ['product' => 'Bookcase', 'price' => 150],
    ['product' => 'Door', 'price' => 100],
]);

$filtered = $collection->whereNotIn('price', [150, 200]);

$filtered->all();

Answer:

<?php

/*
    [
        ['product' => 'Chair', 'price' => 100],
        ['product' => 'Door', 'price' => 100],
    ]
*/

如果我要使用 strict 模式的 `whereNotInStrict`, 可以使用哪個 method？

whereNotInStrict()

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'Desk'],
    ['name' => null],
    ['name' => 'Bookcase'],
]);

$filtered = $collection->whereNotNull('name');

$filtered->all();

Answer:

<?php

/*
    [
        ['name' => 'Desk'],
        ['name' => 'Bookcase'],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect([
    ['name' => 'Desk'],
    ['name' => null],
    ['name' => 'Bookcase'],
]);

$filtered = $collection->whereNull('name');

$filtered->all();

Answer:

<?php

/*
    [
        ['name' => null],
    ]
*/

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = Collection::wrap('John Doe');

$collection->all();
// 這裡的輸出是？

$collection = Collection::wrap(['John Doe']);

$collection->all();
// 這裡的輸出是？

$collection = Collection::wrap(collect('John Doe'));

$collection->all();
// 這裡的輸出是？

Answer:

<?php

// ['John Doe']

// ['John Doe']

// ['John Doe']

以下的 Laravel Collections example 中, 輸出是？

Example:

<?php
$collection = collect(['Chair', 'Desk']);

$zipped = $collection->zip([100, 200]);

$zipped->all();

Answer:
<?php

// [['Chair', 100], ['Desk', 200]]

Higher Order Messages

Laravel Collections method 中, 什麼是 higher order message？

collection method 的縮寫

Lazy Collections

Introduction

以下的 Laravel example code 的意思是？

Example:

<?php
$users = App\User::cursor()->filter(function ($user) {
    return $user->id > 500;
});

foreach ($users as $user) {
    echo $user->id;
}

Answer:
cursor 為 PHP generator 的概念, 不會一次性的將所有 model 都 load 到 memory, 會一次 load 一個 model 並執行, 減低記憶體用量

Lazy Collection Methods

解釋以下 collection example

Example:

<?php
$lazyCollection = LazyCollection::times(INF)->tapEach(function ($value) {
    dump($value);
});

// Nothing has been dumped so far...

$array = $lazyCollection->take(3)->all();

// 1
// 2
// 3

Answer:

<?php
// 宣告一個無窮大的 collection, 但此 collection 必不會執行, 會等到被呼叫才會執行, tapEach 是 lazy collection 專屬的 method
$lazyCollection = LazyCollection::times(INF)->tapEach(function ($value) {
    dump($value);
});

// Nothing has been dumped so far...

// 這邊才會執行
$array = $lazyCollection->take(3)->all();

// 1
// 2
// 3

回答以下 lazy collection example 中的問題

Example:

<?php
$users = User::cursor()->remember();

// 到此, 有 query 被執行嗎？

$users->take(5)->all();

// 到此, 有 query 被執行嗎？
// 哪些 user 被從資料庫拉出？

$users->take(20)->all();

// 到此, 哪些 user 被從資料庫拉出？

Answer:

<?php
$users = User::cursor()->remember();

// 到此, 有 query 被執行嗎？ 沒有

$users->take(5)->all();

// 到此, 有 query 被執行嗎？ 有哦
// 哪些 user 被從資料庫拉出？ 前 5 個 user

$users->take(20)->all();

// 到此, 哪些 user 被從資料庫拉出？ 6 到 20, 前 5 個來自於 cache

#Laravel #Laravel Documentation #Laravel Collections

Laravel - Digging Deeper - Collections

前言

Introduction

Laravel Collections 中, 以下的 Example 的意思是？

Extending Collections

Laravel Collections 中, 如果我要自定義一個 collection method, 在以下的 example 中, 該使用哪個 method?

Available Methods

Laravel Collections 中, 以下的 collection method 的輸出是？

Laravel Collections 中, 以下的 collection example 中, $average 的值是？

Laravel Collections 中, 以下的 collection example 中, $average 的值是？

Laravel Collections 中, 以下的 collection example 中, $chunks 的值是？

Laravel Collections 中, 以下的 collection example 中, $collapsed 的值是？

Laravel Collections 中, 以下的 collection example 中, $combined 的值是？

Laravel Collections 中, 以下的 collection example 中, $collectionB 的值是？

以下的 Laravel example code 的意思是？

Laravel Collections 中, 以下的 collection example 中, $concatenated 的值是？

Laravel Collections 中, 以下的 example 中, 輸出是？

Laravel Collections 中, 以下的 example 中, 輸出是？

Laravel Collections 中, 以下的 example 中, 輸出是？

以下的 Laravel Collections example 中, 邏輯是？

以下的 Laravel Collections example 中, 如果我要 判斷該 collection 中是否有大於 3 的 value, 該在 contains method 中帶入什麼參數？

Laravel collection method contains() 是使用 loose comparison 還是 strict comparison?

Laravel collection method contains() 跟 containsStrict() 差別是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 邏輯是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections method duplicates 跟 duplicatesStrict 差別在於？？

以下的 Laravel Collections method 中, foeach 相當於哪個 collection method?？

以下的 Laravel Collections method each 中, 在以下的 example, 如果我要打斷 iteration, 該怎麼做？

以下的 Laravel example code 的意思是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

Laravel collection method reject 跟 forget 差別是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, forPage method 的 argument 代表的意思是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

Laravel collection method contains 與 has 的差異是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel example code 的意思是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

以下的 Laravel Collections example 中, 輸出是？

**以下的 Laravel Collections example 中, 如果我要判斷該 collection 中是否有大於 3 的 value, 該在 contains method 中帶入什麼參數？**

**Laravel collection method contains() 跟 containsStrict() 差別是？**

**以下的 Laravel Collections method duplicates 跟 duplicatesStrict 差別在於？？**

**以下的 Laravel Collections method each 中, 在以下的 example, 如果我要打斷 iteration, 該怎麼做？**

**Laravel collection method reject 跟 forget 差別是？**

**Laravel collection method contains 與 has 的差異是？**

**Laravel collection method map() 與 transform(), 差別在於？**

Laravel Collections method `some()` 是哪一個 method 的 alias？

Laravel Collections method `sort()` 是否會保留原本的 index？

Laravel Collections method `slice()` 是否會保留原本的 index？

Laravel Collections method 中, `sortBy` 跟 `sortByDesc` 差別在哪？