使用 whereInstanceOf 按类型过滤集合对象

Laravel 的 whereInstanceOf 方法提供了一个基于对象类型过滤集合的整洁方式，当使用多态关联或者混合类型对象集合时特别有用。

<?php
 
use App\Models\User;
use App\Models\Post;
use App\Models\Comment;
use Illuminate\Support\Collection;
 
$collection = collect([
    new User(['name' => 'John']),
    new Post(['title' => 'Hello']),
    new User(['name' => 'Jane']),
]);
$users = $collection->whereInstanceOf(User::class);

让我们探讨一个处理具有不同类型活动的通知提要的实际示例：

<?php
 
namespace App\Services;
 
use App\Models\Comment;
use App\Models\Like;
use App\Models\Follow;
use Illuminate\Support\Collection;
 
class ActivityFeedService
{
    public function getUserFeed(User $user): array
    {
        // Get all activities
        $activities = collect([
            ...$user->comments()->latest()->limit(5)->get(),
            ...$user->likes()->latest()->limit(5)->get(),
            ...$user->follows()->latest()->limit(5)->get(),
        ]);
        // Sort all activities by created_at
        $activities = $activities->sortByDesc('created_at');
 
        return [
            'comments' => $activities->whereInstanceOf(Comment::class)
                ->map(fn (Comment $comment) => [
                    'type' => 'comment',
                    'text' => $comment->body,
                    'post_id' => $comment->post_id,
                    'created_at' => $comment->created_at
                ]),
            'likes' => $activities->whereInstanceOf(Like::class)
                ->map(fn (Like $like) => [
                    'type' => 'like',
                    'post_id' => $like->post_id,
                    'created_at' => $like->created_at
                ]),
            'follows' => $activities->whereInstanceOf(Follow::class)
                ->map(fn (Follow $follow) => [
                    'type' => 'follow',
                    'followed_user_id' => $follow->followed_id,
                    'created_at' => $follow->created_at
                ])
        ];
    }
}

whereInstanceOf 简化了集合中基于类型的过滤，使其更容易处理混合对象类型，同时保持代码整洁、可读。