typescript - angular2 中未定义 http

Question

我正在尝试对我的其他本地主机服务器进行 REST Api 调用，我已经提供了此服务:

import {Injectable} from 'angular2/core';
import {Http} from 'angular2/http';
import {GlobalService} from '../app.service';

@Injectable()
export class AuthenticationService {
    constructor(private _globals: GlobalService) {}
    constructor(private _http: Http) {}
    globals = this._globals.getGlobals()

    getAuthenticationData() {
        this._http.get(globals.apiURL)
    }
}

并在我的组件中调用它:

import { Component } from 'angular2/core';
import {AuthenticationService} from '../services/authentication.service';

@Component({
    selector: 'wd-header';
    templateUrl: 'app/templates/header.html'
    providers: [AuthenticationService]
})

export class HeaderComponent {
    constructor(private _authenticationService: AuthenticationService) {}
    authentication = this._authenticationService.getAuthenticationData()
}

但是由于某些原因，Angular 声称 Http 是未定义的:

EXCEPTION: Error during instantiation of HeaderComponent!. angular2.dev.js:22911:9

ORIGINAL EXCEPTION: TypeError: this._http is undefined

我做错了什么？

编辑以包含 main.ts:

import {bootstrap}    from 'angular2/platform/browser';

import {ROUTER_PROVIDERS} from 'angular2/router';
import {HTTP_PROVIDERS} from 'angular2/http';
import {App} from './app.component';
import {GlobalService} from './app.service';

bootstrap(App, [
    ROUTER_PROVIDERS,
    HTTP_PROVIDERS,
    GlobalService
]);

Answer 1

我将以这种方式重构您的服务代码:

@Injectable()
export class AuthenticationService {
  constructor(private _globals: GlobalService, private _http: Http) {
    this.globals = this._globals.getGlobals();
  }

  getAuthenticationData() {
    return this._http.get(this.globals.apiURL);
  }
}

您的服务只需要一个构造函数，并将全局属性初始化到该构造函数中。

还要小心使用“this”关键字从类本身引用类属性。