Fifteen commonly used Laravel collections (Collection)-Laravel-php.cn

Fifteen commonly used Laravel collections (Collection)

Laravel Eloquent usually returns a collection as a result, which contains many useful and powerful methods. You can easily filter and modify the collection. In this tutorial, let’s take a look at the common methods and functions of collections.
Collections are not limited to eloquent and can also be used alone. But the result of Eloquent is a collection. You can use the helper function collect to convert an array into a collection. The collection methods listed below apply both to eloquent results and to the collection itself.

Let’s say you have a Post model. You found all posts in the php category.

$posts = App\Post::where('category', 'php')->get();

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The above command returns a collection. Collection is a laravel class which uses array functions internally and adds many functionalities to them.

You can simply create a collection using the collect method, as follows:

$collection = collect([
    [
        'user_id' => '1',
        'title' => 'Helpers in Laravel',
        'content' => 'Create custom helpers in Laravel',
        'category' => 'php'
    ],
    [
        'user_id' => '2',
        'title' => 'Testing in Laravel',
        'content' => 'Testing File Uploads in Laravel',
        'category' => 'php'
    ],
    [
        'user_id' => '3',
        'title' => 'Telegram Bot',
        'content' => 'Crypto Telegram Bot in Laravel',
        'category' => 'php'
    ],
]);

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The above array is actually the value of the Post model. In this tutorial we will use this array for simplification. Remember, everything will be based on eloquent in the same way.

When we use the helper method on the eloquent collection, the database will not be queried again. We first want to get all the results from the database, then we use collection methods to filter and modify them without querying the database.

filter()

filter, one of the most useful laravel collection methods, allows you to filter the collection using callbacks. It only passes those items that return true. All other items are deleted. filter Returns a new instance without changing the original instance. It accepts value and key as two parameters in the callback.

$filter = $collection->filter(function($value, $key) {
    if ($value['user_id'] == 2) {
        return true;
    }
});

$filter->all();

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all Method returns the underlying array. The above code returns the following response.

[
    1 => [
        "user_id" => 2,
        "title" => "Testing in Laravel",
        "content" => "Testing File Uploads in Laravel",
        "category" => "php"
    ]
]

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search()

search method searches a collection using a given value. If the value is in the collection, the corresponding key will be returned. If no data item matches the corresponding value, false will be returned.

$names = collect(['Alex', 'John', 'Jason', 'Martyn', 'Hanlin']);

$names->search('Jason');

// 2

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search method uses loose comparison by default. You can pass true in its second parameter to use strict comparison.

You can also pass your own callback function to the search method. Will return the key of the first item that passes the callback's truth test.

$names = collect(['Alex', 'John', 'Jason', 'Martyn', 'Hanlin']);

$names->search(function($value, $key) {
    return strlen($value) == 6;
});

// 3

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chunk()

chunk method splits a collection into multiple smaller collections of a given size. Very useful for displaying collections into a grid.

$prices = collect([18, 23, 65, 36, 97, 43, 81]);

$prices = $prices->chunk(3);

$prices->toArray();

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The above code generates the effect.

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dump()

dump Method to print a collection. It can be used for debugging and finding content within a collection at any location.

$collection->whereIn('user_id', [1, 2])
    ->dump()
    ->where('user_id', 1);

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dump Results of the above code.

Fifteen commonly used Laravel collections (Collection)

map()

map method is used to traverse the entire collection. It accepts callback as parameter. value and key are passed to the callback. Callbacks can modify values and return them. Finally, a new collection instance of the modified item is returned.

$changed = $collection->map(function ($value, $key) {
    $value['user_id'] += 1;
    return $value;
});

return $changed->all();

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Basically, it increases user_id by 1.

The response to the above code is as follows.

[
    [
        "user_id" => 2,
        "title" => "Helpers in Laravel",
        "content" => "Create custom helpers in Laravel",
        "category" => "php"
    ],
    [
        "user_id" => 3,
        "title" => "Testing in Laravel",
        "content" => "Testing File Uploads in Laravel",
        "category" => "php"
    ],
    [
        "user_id" => 4,
        "title" => "Telegram Bot",
        "content" => "Crypto Telegram Bot in Laravel",
        "category" => "php"
    ]
];

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zip()

The Zip method merges the values of the given array with the values of the collection. Values with the same index are added together, which means that the first value of the array is merged with the first value of the collection. Here, I'll use the collection we just created above. This also works for Eloquent collections.

$zipped = $collection->zip([1, 2, 3]);

$zipped->all();

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The JSON response will look like this.

Fifteen commonly used Laravel collections (Collection)

So, basically that’s it. If the length of the array is less than the length of the collection, Laravel will add null to the end of the remaining elements of type Collection. Similarly, if the length of the array is greater than the length of the collection, Laravel will add null to elements of type Collection, followed by the array value.

whereNotIn()

You can use the whereNotIn method to simply filter a collection by key values that are not contained in the given array. It's basically the opposite of whereIn. Additionally, this method uses relaxed comparison == when matching values.

Let's filter $collection where user_id is neither 1 nor 2.

$collection->whereNotIn('user_id', [1, 2]);

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The above statement will only return the last item in $collection. The first parameter is the key and the second parameter is the value array. In the case of eloquent, the first parameter will be the name of the column and the second parameter will be an array of values.

max()

max method returns the maximum value for the given key. You can find the largest user_id by calling max. It's usually used for comparisons like prices or any other number, but for demonstration purposes, let's use user_id. It can also be used with strings, in this case, Z> a.

$collection->max('user_id');

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上面的语句将返回最大的 user_id，在我们的例子中是 3。

pluck()

pluck 方法返回指定键的所有值。它对于提取一列的值很有用。

$title = $collection->pluck('title');
$title->all();

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结果看起来像这样。

[
  "Helpers in Laravel",
  "Testing in Laravel",
  "Telegram Bot"
]

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使用 eloquent 时，可以将列名作为参数传递以提取值。 pluck 也接受第二个参数，对于 eloquent 的集合，它可以是另一个列名。它将导致由第二个参数的值作为键的集合。

$title = $collection->pluck('user_id', 'title');
$title->all();

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结果如下：

[
    "Helpers in Laravel" => 1,
    "Testing in Laravel" => 2,
    "Telegram Bot" => 3
]

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each()

each 是一种迭代整个集合的简单方法。它接受一个带有两个参数的回调：它正在迭代的项和键。 Key 是基于 0 的索引。

$collection->each(function ($item, $key) {
    info($item['user_id']);
});

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上面代码，只是记录每个项的 user_id。

在迭代 eloquent 集合时，您可以将所有列值作为项属性进行访问。以下是我们如何迭代所有帖子。

$posts = App\Post::all();

$posts->each(function ($item, $key) {
    // Do something
});

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如果回调中返回 false，它将停止迭代项目。

$collection->each(function ($item, $key) {
    // Tasks
    if ($key == 1) {
        return false;
    }
});

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tap()

tap() 方法允许你随时加入集合。它接受回调并传递并将集合传递给它。您可以对项目执行任何操作，而无需更改集合本身。因此，您可以在任何时候使用tap来加入集合，而不会改变集合。

$collection->whereNotIn('user_id', 3)
    ->tap(function ($collection) {
        $collection = $collection->where('user_id', 1);
        info($collection->values());
    })
    ->all();

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在上面使用的 tap 方法中，我们修改了集合，然后记录了值。您可以对 tap 中的集合做任何您想做的事情。上面命令的响应是：

[
    [
        "user_id" => "1",
        "title" => "Helpers in Laravel",
        "content" => "Create custom helpers in Laravel",
        "category" => "php"
    ],
    [
        "user_id" => "2",
        "title" => "Testing in Laravel",
        "content" => "Testing File Uploads in Laravel",
        "category" => "php"
    ]
]

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你可以看到 tap 不会修改集合实例。

pipe()

pipe 方法非常类似于 tap 方法，因为它们都在集合管道中使用。 pipe 方法将集合传递给回调并返回结果。

$collection->pipe(function($collection) {
    return $collection->min('user_id');
});

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上述命令的响应是 1。如果从 pipe回调中返回集合实例，也可以链接其他方法。

contains()

contains 方法只检查集合是否包含给定值。只传递一个参数时才会出现这种情况。

$contains = collect(['country' => 'USA', 'state' => 'NY']);

$contains->contains('USA');
// true

$contains->contains('UK');
// false

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如果将键 / 值对传递给 contains 方法，它将检查给定的键值对是否存在。

$collection->contains('user_id', '1');
// true

$collection->contains('title', 'Not Found Title');
// false

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您还可以将回调作为参数传递给回调方法。将对集合中的每个项目运行回调，如果其中任何一个项目通过了真值测试，它将返回 true 否则返回 false。

$collection->contains(function ($value, $key) {
    return strlen($value['title']) <p>回调函数接受当前迭代项和键的两个参数值。 这里我们只是检查标题的长度是否小于13。在 <code>Telegram Bot</code> 中它是12，所以它返回 <code>true</code>。</p><h2>forget()</h2><p><code>forget</code> 只是从集合中删除该项。 您只需传递一个键，它就会从集合中删除该项目。</p><pre class="brush:php;toolbar:false">$forget = collect(['country' => 'usa', 'state' => 'ny']);

$forget->forget('country')->all();

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上面代码响应如下：

[
    "state" => "ny"
]

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forget 不适用于多维数组。

avg()

avg 方法返回平均值。你只需传递一个键作为参数，avg 方法返回平均值。你也可以使用 average 方法，它基本上是 avg 的别名。

$avg = collect([
    ['shoes' => 10],
    ['shoes' => 35],
    ['shoes' => 7],
    ['shoes' => 68],
])->avg('shoes');

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上面的代码返回 30 ，这是所有四个数字的平均值。如果你没有将任何键传递给avg 方法并且所有项都是数字，它将返回所有数字的平均值。如果键未作为参数传递且集合包含键/值对，则 avg 方法返回 0。

$avg = collect([12, 32, 54, 92, 37]);

$avg->avg();

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上面的代码返回 45.4，这是所有五个数字的平均值。

您可以使用这些 laravel 集合方法在您自己的项目中处理集合。

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