Eloquent：集合

简介

默认情况下 Eloquent 返回的都是一个 Illuminate\Database\Eloquent\Collection 对象的实例，包含通过 get 方法或是访问一个关联来获取到的结果。Eloquent 集合对象继承了 Laravel 集合基类，因此它自然也继承了许多可用于与 Eloquent 模型交互的方法。

当然，所有集合都可以作为迭代器，来让你像遍历一个 PHP 数组一样来遍历一个集合：

$users = App\User::where('active', 1)->get();

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

然而，集合比数组更强大的地方是其使用了各种 map / reduce 的直观操作。例如，我们移除所有未激活的用户模型和收集其余各个用户的名字：

$users = App\User::where('active', 1)->get();

$names = $users->reject(function ($user) {
    return $user->active === false;
})
->map(function ($user) {
    return $user->name;
});

可用的方法

集合对象

所有 Eloquent 集合都继承了 Laravel 集合 对象。因此，他们也继承了所有集合类提供的强大的方法：

[all](./collections#method-all) [chunk](./collections#method-chunk) [collapse](./collections#method-collapse) [contains](./collections#method-contains) [count](./collections#method-count) [diff](./collections#method-diff) [each](./collections#method-each) [every](./collections#method-every) [filter](./collections#method-filter) [first](./collections#method-first) [flatten](./collections#method-flatten) [flip](./collections#method-flip) [forget](./collections#method-forget) [forPage](./collections#method-forpage) [get](./collections#method-get) [groupBy](./collections#method-groupby) [has](./collections#method-has) [implode](./collections#method-implode) [intersect](./collections#method-intersect) [isEmpty](./collections#method-isempty) [keyBy](./collections#method-keyby) [keys](./collections#method-keys) [last](./collections#method-last) [map](./collections#method-map) [merge](./collections#method-merge) [pluck](./collections#method-pluck) [pop](./collections#method-pop) [prepend](./collections#method-prepend) [pull](./collections#method-pull) [push](./collections#method-push) [put](./collections#method-put) [random](./collections#method-random) [reduce](./collections#method-reduce) [reject](./collections#method-reject) [reverse](./collections#method-reverse) [search](./collections#method-search) [shift](./collections#method-shift) [shuffle](./collections#method-shuffle) [slice](./collections#method-slice) [sort](./collections#method-sort) [sortBy](./collections#method-sortby) [sortByDesc](./collections#method-sortbydesc) [splice](./collections#method-splice) [sum](./collections#method-sum) [take](./collections#method-take) [toArray](./collections#method-toarray) [toJson](./collections#method-tojson) [transform](./collections#method-transform) [unique](./collections#method-unique) [values](./collections#method-values) [where](./collections#method-where) [whereLoose](./collections#method-whereloose) [zip](./collections#method-zip)

自定义集合

如果你需要使用一个自定义的 Collection 对象到自己的扩充方法上，则可以在模型中重写 newCollection 方法：

<?php

namespace App;

use App\CustomCollection;
use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    /**
     * 创建一个新的 Eloquent 集合实例。
     *
     * @param  array  $models
     * @return \Illuminate\Database\Eloquent\Collection
     */
    public function newCollection(array $models = [])
    {
        return new CustomCollection($models);
    }
}

一旦你定义了 newCollection 方法，则可在任何 Eloquent 返回该模型的 Collection 实例时，接收到一个你的自定义集合的实例。如果你想要在应用程序的每个模型中使用自定义集合，则应该在所有的模型继承的模型基类中重写 newCollection 方法。

本译文转载自 Laravel China 社区 组织翻译的 Laravel 中文文档。原文链接：https://learnku.com/docs/laravel/5.1/eloquent-collections/1086