书香隽秀 - Collections
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link: https://www.huangshuxiu.com/tag/Collections/
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Collections
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date: 2023-05-25T09:00:00+08:00
description: CollectionsIntroductionThe Illuminate\Support\Collection class provides a fluent, convenient wrapper for working with arrays of data. For example, check out the following code. We'll use the collect helper to create a new collection instance from the array, run the strtoupper function on each element, and then remove all empty elements:$collection = collect(['taylor', 'abigail', null])->map(function ($name) { return strtoupper($name); })->reject(function ($name) { return empty($name); });As you can see, the Collection class allows you to chain its methods to perform fluent mapping and reducing of the underlying array. In general, collections are immutable, meaning every Collection method returns an entirely new Collection instance.Creating CollectionsAs mentioned above, the collect helper returns a new Illuminate\Support\Collection instance for the given array. So, creating a collection is as simple as:$collection = collect([1, 2, 3]);The results of Eloquent queries are always returned as Collection instances.Extending CollectionsCollections are "macroable", which allows you to add additional methods to the Collection class at run time. The Illuminate\Support\Collection class' macro method accepts a closure that will be executed when your macro is called. The macro closure may access the collection's other methods via $this, just as if it were a real method of the collection class. For example, the following code adds a toUpper method to the Collection class: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']Typically, you should declare collection macros in the boot method of a service provider.Macro ArgumentsIf necessary, you may define macros that accept additional arguments:use Illuminate\Support\Collection; use Illuminate\Support\Facades\…