Question

在完成教程之后，我试图在组件中注入服务：

import { Component } from '@angular/core';
import { TodoService } from './todos.service';
import { ITodo } from './todo';
import { Http , Response } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/map';

@Component({
  selector: 'my-app',
  templateUrl: `app/app.component.html`,
  providers: [TodoService]
})
export class AppComponent  
{ 
  itodos: ITodo[];
  appTitle: string = 'To Do App';
  constructor(private _todo: TodoService);

  ngOnInit() : void {
     this._todo.gettodos()
     .subscribe(itodos => this.itodos = itodos);
  }
}

在调用TodoService时，出现“缺少构造函数实现”

我的服务：

import { Injectable } from '@angular/core';
import { Http , Response } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/do';
import { ITodo } from './todo';

@Injectable()
export class TodoService {
   private _todoUrl='app/todos.json';
   constructor(private _http: Http){}

   gettodos(): Observable<ITodo[]> {
      return this._http.get(this._todoUrl)
      .map((response: Response) => <ITodo[]> response.json())
      .do(data => console.log(JSON.stringify(data)));
   }
}

由于我的TodoService使用Http，我该怎么做才能清除错误？

Answer 1

您的构造函数没有主体，如果您不想在构造函数中有任何多余的代码，只需提供一个空主体

constructor(private _todo: TodoService){}

Angular-缺少构造函数实现

1 个答案: