Angular/TypeScript中能否在Mixin中使用依赖注入？

现有代码 #

export const MyMixin = <T extends Type<MyClass>>(Base: T): T =>
  class extends Base {
    constructor(...args: any[]) {
      super(...args);
    }
  };

尝试添加依赖后的代码 #

需要给Mixin添加依赖Service的myMethod()，修改后代码如下：

export const MyMixin = <T extends Type<MyClass>>(Base: T): T =>
    class extends Base {
      constructor(private injector: Injector, ...args: any[]) { // 👈 触发TS错误(2545)
        super(...args);
        this.myMethod();
      }

      private myMethod(): void {
        this.injector.get(SomeService).doSomething();
      };
    };

TypeScript报错信息 #

A mixin class must have a constructor with a single rest parameter of type 'any[]'.ts(2545)

此前有类似问题，现有方案是为全局类提供Injector，但属于反模式，现寻求Mixin中实现“干净”依赖注入的方案。

解决方案：符合规则的干净实现方式 #

方案1：利用父类注入的服务实例 #

确保父类MyClass已注入所需服务，Mixin直接通过继承链访问父类的服务实例，完全遵循TypeScript的Mixin构造函数规则：

// 父类MyClass
export class MyClass {
  constructor(protected someService: SomeService) {}
}

// Mixin实现
export const MyMixin = <T extends Type<MyClass>>(Base: T): T =>
  class extends Base {
    constructor(...args: any[]) {
      super(...args);
      this.myMethod();
    }

    private myMethod(): void {
      this.someService.doSomething();
    }
  };

方案2：从构造函数参数中提取Injector #

如果父类已注入Injector，可以从Mixin构造函数的rest参数中提取该实例，避免修改构造函数签名：

import { Injector, Type } from '@angular/core';

export const MyMixin = <T extends Type<MyClass>>(Base: T): T =>
  class extends Base {
    private injector: Injector;

    constructor(...args: any[]) {
      super(...args);
      // 从父类构造参数中筛选出Injector实例
      this.injector = args.find(arg => arg instanceof Injector) as Injector;
      this.myMethod();
    }

    private myMethod(): void {
      const someService = this.injector.get(SomeService);
      someService.doSomething();
    }
  };

方案3：将服务作为Mixin参数传入 #

定义Mixin时直接接收所需服务实例，把注入逻辑移到Mixin外部，保持Mixin的纯净性：

import { Type } from '@angular/core';
import { SomeService } from './some.service';

export const MyMixin = <T extends Type<MyClass>>(Base: T, someService: SomeService): T =>
  class extends Base {
    constructor(...args: any[]) {
      super(...args);
      this.myMethod(someService);
    }

    private myMethod(someService: SomeService): void {
      someService.doSomething();
    }
  };

使用时在组件/类中注入服务后传入Mixin：

@Component({...})
export class MyComponent extends MyMixin(MyClass, someService) {
  constructor(private someService: SomeService) {
    super(someService);
  }
}

内容的提问来源于stack exchange，提问作者jaheraho