组件钩子

全局组件钩子

若要为应用中每一个组件添加功能或行为，可以使用 Livewire「组件钩子」（Component Hooks）。

组件钩子允许你定义一个类，从外部挂接到 Livewire 组件的生命周期（不在组件类本身上，也不在 trait 中）。

在看实际示例之前，先看一个通用的组件钩子类，其中列出了内部可用的全部方法：

use Livewire\ComponentHook;

class MyComponentHook extends ComponentHook
{
    public static function provide()
    {
        // Runs once at application boot.
        // Can be used to register any services you may need.
    }

    public function mount($params, $parent)
    {
        // Called when a component is "mounted"
        // 
        // $params: Array of parameters passed into the component
        // $parent: The parent component object if this is a nested component
    }

    public function hydrate($memo)
    {
        // Called when a component is "hydrated"
        //
        // $memo: An associative array of the "dehydrated" metadata for this component
    }

    public function boot()
    {
        // Called when the component boots
    }

    public function update($property, $path, $value)
    {
        // Called before the component updates...

        return function () {
            // Called after the component property has updated...
        };
    }

    public function call($method, $params, $returnEarly)
    {
        // Called before a method on the component is called...

        return function ($returnValue) {
            // Called after a method is called
        };
    }

    public function render($view, $data)
    {
        // Called after "render" is called but before the Blade has been rendered...
        return function ($html) {
            // Called after the component's view has been rendered
        };
    }

    public function dehydrate($context)
    {
        // Called when a component "dehydrates"
    }

    public function exception($e, $stopPropagation)
    {
        // Called if an exception is thrown within a component...
    }
}

可在服务提供者（如 App\Providers\AppServiceProvider）中注册组件钩子，例如：

<?php

namespace App\Providers;

use Illuminate\Support\ServiceProvider;
use Livewire\Livewire;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     */
    public function boot(): void
    {
        Livewire::componentHook(MyComponentHook::class);
    }

    // ...
}

看完组件钩子的概览后，下面是一个更实用的例子：用它们为应用提供有用功能。

假设你希望任意 Livewire 动作都能返回 CSV，并自动触发文件下载。例如，可在 CreatePost 组件的 save 方法中返回 Csv：

use Livewire\Component;

class CreateUser extends Component
{
    public $username = '';

    public $email = '';

    public function something()
    {
        return new Csv();
    }

    // ...
}

<?php

namespace App;

use Livewire\ComponentHook;

class SupportCsvDownloads extends ComponentHook
{
    public function call($method, $params, $returnEarly)
    {
        // Called before a method on the component is called...

        return function ($returnValue) {
            if ($returnValue instanceof Csv) {
                // do something
            }
        };
    }
}

call() 返回的回调在组件方法执行完毕后运行。本例中，它可以检查每个方法的返回值，并在一处统一处理 Csv 实例。