Question

In this plunk我有一个Angular 6模块，其相关服务包装了HttpClient。该模块由应用程序模块导入，主要的应用程序组件调用该服务。

问题是出现以下错误：

模块声明的意外值'MyHttpService' “ CoreServiceModule”。请添加一个@ Pipe / @ Directive / @ Component 注释

我检查了所有导入和声明，但找不到问题。错误在哪里？

模块：

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { HttpClientModule } from '@angular/common/http';
import { MyHttpService } from './http.service';

@NgModule({
  imports: [
    CommonModule,
    HttpClientModule
  ],
  declarations: [
    MyHttpService
  ],
  exports: [
    MyHttpService
  ]
})
export class CoreServiceModule {}

服务：

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';

@Injectable({
  providedIn: 'root'
})
export class MyHttpService {

  constructor(public httpx: HttpClient) {
        console.log("In the HttpClient constructor - " + this.httpx) 
  }

  call () {
        let data = { x: 1 };
        this.httpx.post('response.json', data).subscribe(result => {
            console.log("Http result = " + result);
          }, error => console.log('There was an error: '));
    }
}

Answer 1

通常如错误所述， services,pipes 应该位于模块的提供者下， remove 来自 declarations 并将其添加到 providers ，

@NgModule({
  imports: [
    CommonModule,
    HttpClientModule
  ]
  declarations : [],
  providers:[ 
     MyHttpService
  ],
  exports: [

  ]
})

Answer 2

声明仅适用于可声明的类

将MyHttpService添加到Providers。

@NgModule({
  imports: [
    CommonModule,
    HttpClientModule
  ]
  providers:[ 
     MyHttpService
  ]
})

Angular 6中模块声明的意外值

2 个答案: