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Question

当我在服务的构造函数中使用Http时，我面临上述错误。

员工服务代码

 import {Component} from '@angular/core'
    import {Injectable} from '@angular/core'
    import { HttpModule } from '@angular/http';
    import {Http, Response} from '@angular/http';
    import {Observable} from 'rxjs/observable';
    import 'rxjs/add/operator/map';



    @Injectable()


    export class employeService{
    constructor(public http : Http){

    }

    getEmployeename() : Observable<string>{

        return         
     this.http.get('http://localhost:53656/api/values/Getdata').map((resp:           
     Response) => resp.json());


      }
    }

注意我在员工组件内直接调用我的服务（不是来自app.module.ts文件）

员工组件代码

  import { Component, OnInit} from '@angular/core';
    import {employeService} from './Service/service';



    @Component({  
      templateUrl: './app.employee.html',

      providers: [ employeService ]
     })

     export class EmployeeComponent implements OnInit{
       empName : string;
       constructor(private empService : employeService){

     }

     ngOnInit(){
      this.empService.getEmployeename().subscribe((empName)=>this.empName = 
      empName);
    }
   }

控制台中的错误消息：

core.js:1598 ERROR Error: Uncaught (in promise): Error:       
StaticInjectorError(AppModule)[employeService -> Http]: 
StaticInjectorError(Platform: core)[employeService -> Http]: 
NullInjectorError: No provider for Http!
Error: StaticInjectorError(AppModule)[employeService -> Http]: 
StaticInjectorError(Platform: core)[employeService -> Http]: 
NullInjectorError: No provider for Http!
at

Answer 1

您需要将HTTPModule导入主模块。

import { HttpModule } from '@angular/http';

@NgModule({
  declarations: [ ],
  imports: [
    ......
    HttpModule
  ]
....

更新

根据最新版本，您应使用HttpClientModule代替HttpModule

像这样导入

import { HttpClientModule } from '@angular/common/http';

@NgModule({
  declarations: [ ],
  imports: [
    ......
    HttpClientModule
  ]
....

Answer 2

在app.module.ts中你应该使用HttpClientModule 还将您的服务提供商导入提供商

未捕获（承诺）：错误：StaticInjectorError（AppModule）[employeService - ＆gt; HTTP]：

2 个答案:

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