Angular2注入器-动态选择服务实现

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

// 定义服务接口
interface MyService {
  doSomething(): void;
}

// 定义两个不同的服务实现
@Injectable()
class ServiceA implements MyService {
  doSomething() {
    console.log('Service A');
  }
}

@Injectable()
class ServiceB implements MyService {
  doSomething() {
    console.log('Service B');
  }
}

// 定义条件提供者
const conditionToken = new InjectionToken<boolean>('condition');

@Injectable()
class ConditionalProvider {
  constructor(private injector: Injector) {}

  getMyService(): MyService {
    const condition = this.injector.get(conditionToken);
    return condition ? this.injector.get(ServiceA) : this.injector.get(ServiceB);
  }
}

// 在模块中配置注入器和条件提供者
@NgModule({
  providers: [
    { provide: conditionToken, useValue: true },
    ConditionalProvider,
    ServiceA,
    ServiceB
  ]
})
class AppModule {}

// 在组件中使用动态选择的服务实现
@Component({
  selector: 'app-root',
  template: `
    <button (click)="doSomething()">Do Something</button>
  `
})
class AppComponent {
  constructor(private conditionalProvider: ConditionalProvider) {}

  doSomething() {
    const myService = this.conditionalProvider.getMyService();
    myService.doSomething();
  }
}