Symfony 7中无法自动注入ValidatorService错误的解决方案

错误信息 #

Cannot autowire service "App\Core\Validator\ValidatorService": argument "$validators" of method "__construct()" references interface "App\Core\Validator\ValidatorInterface" but no such service exists. Did you create an instantiable class that implements this interface?

问题背景 #

我想在服务中注入一个接口的多个实例，已经创建了ValidatorInterface，并在LoginMessageValidator、WelcomeMessageValidator类中实现该接口，同时编写了ValidatorService类（代码如下）。项目使用自动装配，但出现上述错误，请问该如何解决？

相关代码 #

ValidatorInterface.php

<?php declare(strict_types = 1);

namespace App\Core\Validator;

use App\Core\MailStruct;

interface ValidatorInterface
{  
    /**
     * support: checks if the validator class supports this type of email 
     *
     * @param  string $type
     * @return bool
     */
    public function support(string $type): bool;

    /**
     * validate: checks if the request data is valid
     *
     * @param  MailStruct $mail
     * @return void
     */
    public function validate(MailStruct $mail): void;
}

LoginMessageValidator.php

<?php declare(strict_types = 1);

namespace App\Core\Validator;

use App\Core\EmailType;
use App\Core\MailStruct;
use App\Core\Validator\ValidatorInterface;


class LoginMessageValidator implements ValidatorInterface
{
    public function support(string $type): bool
    {
        return $type === EmailType::LOGIN_EMAIL;  
    }

    public function validate(MailStruct $mail): void
    {
        //dd(EmailType::LOGIN_EMAIL);
    }
    
}

WelcomeMessageValidator.php

<?php declare(strict_types = 1);

namespace App\Core\Validator;

use App\Core\EmailType;
use App\Core\MailStruct;
use App\Core\Validator\ValidatorInterface;

class WelcomeMessageValidator implements ValidatorInterface
{
    public function support(string $type): bool
    {
        return $type === EmailType::WELCOME_EMAIL;  
    }

    public function validate(MailStruct $mail): void
    {
        dd(EmailType::WELCOME_EMAIL);
    }
    
}

ValidatorService.php（原错误版本）

<?php declare(strict_types = 1);

namespace App\Core\Validator;

use App\Core\MailStruct;
use App\Core\Validator\ValidatorInterface;

class ValidatorService
{

    private ValidatorInterface $validators;

    public function __construct(ValidatorInterface $validators)
    {
        $this->validators = $validators;    
    }
    
    public function validate(MailStruct $mail)
    {
        foreach($this->validators as $validator){
            $validator->validate($mail);
        }
    }
}

解决方法 #

1. 修改ValidatorService的类型声明 #

你当前的代码试图把多个验证器实例注入到单个ValidatorInterface类型的参数中，这不符合依赖注入规则——单个接口类型参数只会尝试注入一个实现类，而Symfony找不到直接对应ValidatorInterface的服务（因为接口本身不能实例化）。

需要把参数类型改成可迭代类型（iterable），同时调整属性类型：

<?php declare(strict_types = 1);

namespace App\Core\Validator;

use App\Core\MailStruct;
use App\Core\Validator\ValidatorInterface;

class ValidatorService
{
    // 把单个接口类型改成可迭代类型
    private iterable $validators;

    // 构造函数参数同样改为iterable
    public function __construct(iterable $validators)
    {
        $this->validators = $validators;    
    }
    
    public function validate(MailStruct $mail)
    {
        // 遍历所有验证器，只执行支持当前邮件类型的验证逻辑
        foreach($this->validators as $validator){
            if ($validator->support($mail->type)) { // 假设MailStruct有type属性
                $validator->validate($mail);
            }
        }
    }
}

2. 确保Symfony自动收集所有实现类 #

如果使用Symfony 4.3及以上版本，自动装配会自动识别所有实现ValidatorInterface的服务，并将它们注入到iterable类型的参数中，无需额外配置。

如果是旧版本，需要在config/services.yaml中添加标签配置，让Symfony收集所有验证器：

services:
    # 给所有实现ValidatorInterface的类打上标签
    _instanceof:
        App\Core\Validator\ValidatorInterface:
            tags: ['app.email_validator']

    # 给ValidatorService注入所有带该标签的服务
    App\Core\Validator\ValidatorService:
        arguments:
            $validators: !tagged_iterator app.email_validator

3. 验证逻辑优化（可选） #

原代码的validate方法会遍历所有验证器并执行validate，但你的每个验证器都有support方法，应该只对当前邮件类型匹配的验证器执行验证，这样更符合设计意图（上面修改后的代码已经包含这部分逻辑）。

内容的提问来源于stack exchange，提问作者Templator Khan