Laravel/Lumen中控制器构造函数与中间件的执行顺序及状态管理

<?php

namespace App\Http\Controllers;

use Laravel\Lumen\Routing\Controller;

class IndexController extends Controller
{
    public function __construct()
    {
        echo '1'; // 构造函数开始执行
        $this->middleware('lang'); // 注册中间件
        echo '3'; // 构造函数继续执行
    }

    public function home()
    {
        return 'Home Page';
    }
}

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;

class LangMiddleware
{
    public function handle(Request $request, Closure $next)
    {
        echo '2'; // 中间件的handle方法执行
        return $next($request);
    }
}

<?php

namespace App\Helpers;

class Translator
{
    private $scope;
    private $lang;
    private $translations = [
        'en' => ['home' => ['welcome' => 'Welcome to our site!']],
        'fr' => ['home' => ['welcome' => 'Bienvenue sur notre site!']],
        'es' => ['home' => ['welcome' => '¡Bienvenido a nuestro sitio!']],
    ];

    public function __construct(string $scope, string $lang = 'en')
    {
        $this->scope = $scope;
        $this->lang = $lang;
    }

    public function get(string $key): ?string
    {
        return $this->translations[$this->lang][$this->scope][$key] ?? null;
    }
}

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;

class LangMiddleware
{
    public function handle(Request $request, Closure $next)
    {
        // 假设语言通过请求参数 'lang' 传入，默认为 'en'
        $lang = $request->input('lang', 'en'); 
        // 也可以硬编码，如原问题所示
        // $lang = 'fr'; 

        // 将语言设置到全局配置中，通常使用 'app.locale'
        config(['app.locale' => $lang]);

        return $next($request);
    }
}

<?php

namespace App\Http\Controllers;

use Laravel\Lumen\Routing\Controller;
use App\Helpers\Translator;
use Illuminate\Http\Request; // 引入Request类

class IndexController extends Controller
{
    public function __construct()
    {
        // 仅仅注册中间件，不进行依赖中间件状态的初始化
        $this->middleware('lang');
    }

    public function home(Request $request) // 通过依赖注入获取Request实例
    {
        // 在此处，LangMiddleware已经执行完毕，config('app.locale') 已被设置
        $currentLang = config('app.locale', 'en'); // 获取中间件设置的语言

        // 现在可以安全地初始化Translator实例
        $transhome = new Translator('home', $currentLang);

        return view('home', [
            'transhome' => $transhome,
            'welcomeMessage' => $transhome->get('welcome'),
            'currentLang' => $currentLang,
        ]);
    }
}

$router->get('/home', 'IndexController@home');
// 访问 /home?lang=fr 将会显示法语欢迎语

<?php

namespace App\Http\Controllers;

use Laravel\Lumen\Routing\Controller;
use App\Helpers\Translator;

class IndexController extends Controller
{
    private $transhome; // 声明属性，但不立即初始化

    public function __construct()
    {
        $this->middleware('lang');
    }

    /**
     * 延迟加载Translator实例
     */
    private function getTranshome(): Translator
    {
        if (!$this->transhome) {
            // 只有在第一次访问时才进行初始化
            $currentLang = config('app.locale', 'en');
            $this->transhome = new Translator('home', $currentLang);
        }
        return $this->transhome;
    }

    public function home()
    {
        // 调用延迟加载方法获取Translator实例
        return view('home', [
            'transhome' => $this->getTranshome(),
            'welcomeMessage' => $this->getTranshome()->get('welcome'),
        ]);
    }
}

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;
use App\Helpers\Translator; // 引入Translator类

class LangMiddleware
{
    public function handle(Request $request, Closure $next)
    {
        $lang = $request->input('lang', 'en');
        config(['app.locale' => $lang]);

        // 将Translator实例绑定到服务容器
        app()->singleton(Translator::class, function ($app) use ($lang) {
            return new Translator('global_scope', $lang); // 或根据需要定义scope
        });

        // 如果需要特定scope的Translator，也可以这样绑定
        app()->bind('translator.home', function ($app) use ($lang) {
            return new Translator('home', $lang);
        });

        return $next($request);
    }
}

<?php

namespace App\Http\Controllers;

use Laravel\Lumen\Routing\Controller;
use App\Helpers\Translator; // 引入Translator类

class IndexController extends Controller
{
    private $translator;
    private $homeTranslator;

    // 构造函数中注入，此时LangMiddleware已将Translator绑定到容器
    public function __construct(Translator $translator, Translator $homeTranslator = null) // 注意：如果绑定了'translator.home'，这里需要用别名或工厂方法
    {
        $this->middleware('lang');
        $this->translator = $translator;
        // 如果是绑定了别名，需要手动解析
        $this->homeTranslator = app('translator.home'); 
    }

    public function home()
    {
        return view('home', [
            'globalWelcome' => $this->translator->get('welcome'),
            'homeWelcome' => $this->homeTranslator->get('welcome'),
        ]);
    }
}