使用注入的角度服务作为静态方法中的依赖项

Question

我正在尝试在静态方法中使用注入的依赖项，当然注入的依赖项是实例范围并且不能在静态方法中使用。

这是我的课：

@Injectable()
export class PasswordValidationService {

  constructor(private userAccountService:UserAccountService) {
  }

  static passwordValidator(control:AbstractControl) {
    return control
      .valueChanges
      .debounceTime(400)
      .switchMap(()=> this.userAccountService.checkCurrentPassword(control.value))
      .map(res=> {
          if (res.json() === true) {
            return null;
          }
          else {
            return {invalid: true};
          }
        }
      );
  }

}

我的问题是在静态方法中使用

UserAccountService

（依赖项）的最佳实践是什么？

编辑：我重新设计了我的应用程序，使用实例方法而不是静态方法，如下所示：

这是验证器：

import {Injectable} from "@angular/core";
import {UserAccountService} from "../../useraccount/useraccount.service";
import {AbstractControl} from "@angular/common";
import {Observable} from "rxjs/Observable";


@Injectable()
export class PasswordValidationService {

  constructor(private userAccountService:UserAccountService) {
  }

  passwordValidator(control:AbstractControl):Observable<any> {
    let validationResult = this.userAccountService.checkCurrentPassword(control.value)
      .map(res=> {
          if (res.json() === true) {
            return null;
          }
          else {
            return {invalid: true};
          }
        }
      );

    return validationResult;
  }

}

这是使用验证器的组件：

constructor(private router:Router,
              private formBuilder:FormBuilder,
              private stylingService:StylingService,
              private sessionService:SessionService,
              private passwordValidationService:PasswordValidationService) {
  }

  ngOnInit() {
    this.signinForm = this.formBuilder.group({
      credentials: this.formBuilder.group({
        username: [this.credentials.username, Validators.required],
        password: [this.credentials.password, [Validators.required, this.passwordValidationService.passwordValidator]]
      })
    });
  }

这是我收到的错误消息：

browser_adapter.ts:82 TypeError: Cannot read property 'userAccountService' of undefined
    at PasswordValidationService.passwordValidator (http://localhost:8080/app/shared/services/password-validation.service.js:18:36)
    at eval (http://localhost:8080/vendor/@angular/forms/src/validators.js:137:49)
    at Array.map (native)
    at _executeValidators (http://localhost:8080/vendor/@angular/forms/src/validators.js:137:23)
    at FormControl.eval [as validator] (http://localhost:8080/vendor/@angular/forms/src/validators.js:116:33)
    at FormControl.AbstractControl._runValidator (http://localhost:8080/vendor/@angular/forms/src/model.js:178:56)
    at FormControl.AbstractControl.updateValueAndValidity (http://localhost:8080/vendor/@angular/forms/src/model.js:164:29)
    at new FormControl (http://localhost:8080/vendor/@angular/forms/src/model.js:304:14)
    at FormBuilder.control (http://localhost:8080/vendor/@angular/forms/src/form_builder.js:36:16)
    at FormBuilder._createControl (http://localhost:8080/vendor/@angular/forms/src/form_builder.js:68:25)

Answer 1

要么不要使方法静态，要么从实例方法转发

export class PasswordValidationService {

  constructor(private userAccountService:UserAccountService) {
  }

  validate(control:AbstractControl) {
    return PasswordValidationService.passwordValidator(control);
  }

  static passwordValidator(control:AbstractControl) {
    ...
  }
}

Answer 2

我使用它在应用程序初始化的某个地方将实例设置为静态，然后使用它。

class AppComponent {
    constructor(private barService: BarService{
        BarService.appInstance = barService
    }
}


class FooUtil{

  doSomethingFancy(){
      //you might even check for BarService.appInstance the way you want to handle it
     BarService.appInstance.somethingEvenMoreFancy()
  }

}