使用依赖注入将参数传递给服务的构造函数? [英] Passing parameters to constructor of a service using Dependency Injection?

问题描述

我有自定义服务类:

@Injectable()

export class CustomService {
  constructor(num: number) {
  }
}

此类被注入组件的构造函数中，如下所示:

This class is injected in constructor of component like this:

constructor(private cs: CustomService) {
}

但是如何将参数num传递给上述构造函数中的服务? 像这样的东西:

But how to pass parameter num to service in constructor described above? Something like that:

constructor(private cs: CustomService(1)) {
}

作为解决方案，我可以使用Fabric模式，但是只有一种方法吗?

I know as solution I can use Fabric pattern, but is there only one way to do that?

推荐答案

如果CustomService实例不应该是注入器单例，则为:

If CustomService instances should not be injector singletons, it is:

providers: [{ provide: CustomService, useValue: CustomService }]

...

private cs;

constructor(@Inject(CustomService) private CustomService: typeof CustomService) {
  this.cs = new CustomService(1);
}

如果应该记住CustomService来返回各个参数的单例，则应通过其他缓存服务来检索实例:

If CustomService is supposed be memoized to return singletons for respective parameter, instances should be retrieved through additional cache service:

class CustomServiceStorage {
  private storage = new Map();

  constructor(@Inject(CustomService) private CustomService: typeof CustomService) {}
  get(num) {
    if (!this.storage.has(num))
      this.storage.set(num, new this.CustomService(num));

    return this.storage.get(num);
  }
}

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