Question

所以，我们谈论的是angular2，我知道它仍处于alpha状态。我创建了一个基本服务，我将在另一个服务中使用。然后将后者用于组件中。

基本服务看起来像这样

import {Injectable, Observable} from 'angular2/core';
import {Http} from 'angular2/http';
import {RequestOptionsArgs, Connection, ConnectionBackend} from 'angular2/http';
import {BaseRequestOptions, RequestOptions} from 'angular2/http';
import {RequestMethods} from 'angular2/http';
import {Response} from 'angular2/http';
import {Request} from 'angular2/http';
import {makeTypeError} from 'angular2/src/facade/exceptions';

@Injectable()

export class MyOAuth extends Http {
  constructor(backend: ConnectionBackend, defaultOptions: RequestOptions) {
    super(backend, defaultOptions);
  }

  /**
   * Performs any type of http request. First argument is required, and can either be a url or
   * a {@link Request} instance. If the first argument is a url, an optional {@link RequestOptions}
   * object can be provided as the 2nd argument. The options object will be merged with the values
   * of {@link BaseRequestOptions} before performing the request.
   */
  request(url: string | Request, options?: RequestOptionsArgs): Observable<Response> {
    var responseObservable: any;
    if (isString(url)) {
      responseObservable = httpRequest(
          this._backend,
          new Request(mergeOptions(this._defaultOptions, options, RequestMethods.Get, url)));
    } else if (url instanceof Request) {
      responseObservable = httpRequest(this._backend, url);
    } else {
      throw makeTypeError('First argument must be a url string or Request instance.');
    }
    return responseObservable;
  }
}

使用上述服务的其他服务如下所示（authenticate.js）：

import {Injectable, Inject} from 'angular2/angular2';
import {MyOAuth} from './MyOAuth';


@Injectable()

export class AuthenticationService {

  constructor(@Inject(MyOAuth) http) {
    this.http = http;
  }

  authenticate(username, password, community) {
    console.log('authenticate');
  }
}

然后在课堂上使用这项服务，我称之为：

import {Page} from 'ionic/ionic';
import './login.scss';
import {AuthenticationService} from '../../services/authentication';

@Page({
  templateUrl: 'app/login/login.html',
  providers: [AuthenticationService] //As of alpha 42
})

我在浏览器中遇到的错误是

EXCEPTION: No provider for MyOAuth! (LoginPage -> AuthenticationService -> MyOAuth)

对我来说，我必须导入MyOAuth并不合适...

Answer 1

当您需要将自定义服务注入其他服务时，您需要在更大的上下文（组件，页面，应用程序）中提供服务

你可以这样做：

import {Page} from 'ionic/ionic';
import './login.scss';
import {AuthenticationService} from '../../services/authentication';

@Page({
    templateUrl: 'app/login/login.html',
    providers: [[AuthenticationService], [MyOAuth]]
})

对我来说，如果服务可以在多个地方重用，我总是在应用程序上下文中定义它。例如：

@Component({
    templateUrl: 'build/app.html',
    providers: [[AuthenticationService], [MyOAuth]]
})
class MyApp{
}

所以这些服务只会被设置一次。如果你提供它们，例如：Page1，Page2，它们将被实例化两次

Answer 2

您还需要提供服务：

import {Page} from 'ionic/ionic';
import {provider} from '@angular/core';
import './login.scss';
import {AuthenticationService} from '../../services/authentication';

@Page({
  templateUrl: 'app/login/login.html',
  providers: [AuthenticationService, provide(MyOAuth, {useClass: MyOAuth})]
})

使用使用其他自定义服务的服务时，没有提供商...错误

2 个答案: