Неожиданное значение HttpClient

Question

Это мой файл app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { ErrorHandler, NgModule } from '@angular/core';
import { IonicApp, IonicErrorHandler, IonicModule } from 'ionic-angular';
import { SplashScreen } from '@ionic-native/splash-screen';
import { StatusBar } from '@ionic-native/status-bar';
import { HttpClient } from '@angular/common/http';

import { MyApp } from './app.component';
import { HomePage } from '../pages/home/home';
import { DataProvider } from '../providers/data/data';

@NgModule({
  declarations: [
    MyApp,
    HomePage,
  ],
  imports: [
    BrowserModule,
    HttpClient,
    IonicModule.forRoot(MyApp)
  ],
  bootstrap: [IonicApp],
  entryComponents: [
    MyApp,
    HomePage
  ],
  providers: [
    StatusBar,
    SplashScreen,
    {provide: ErrorHandler, useClass: IonicErrorHandler},
    DataProvider
  ]
})
export class AppModule {}

Я получаю сообщение об ошибке, подобное этому:

Uncaught Error: Unexpected value 'HttpClient' imported by the module
'AppModule'. Please add a @NgModule annotation.
    at syntaxError (compiler.js:486)
    at compiler.js:15240
    at Array.forEach (<anonymous>)
    at CompileMetadataResolver.getNgModuleMetadata (compiler.js:15215)
    at JitCompiler._loadModules (compiler.js:34413)
    at JitCompiler._compileModuleAndComponents (compiler.js:34374)
    at JitCompiler.compileModuleAsync (compiler.js:34268)
    at CompilerImpl.compileModuleAsync (platform-browser-dynamic.js:239)
    at PlatformRef.bootstrapModule (core.js:5578)
    at Object.199 (main.ts:5) syntaxError @ compiler.js:486 (anonymous) @ compiler.js:15240
CompileMetadataResolver.getNgModuleMetadata @ compiler.js:15215
JitCompiler._loadModules @ compiler.js:34413
JitCompiler._compileModuleAndComponents @ compiler.js:34374
JitCompiler.compileModuleAsync @ compiler.js:34268
CompilerImpl.compileModuleAsync @ platform-browser-dynamic.js:239
PlatformRef.bootstrapModule @ core.js:5578 199 @ main.ts:5
__webpack_require__ @ bootstrap c2d88ebb0bb27539f897:54 webpackJsonpCallback @ bootstrap c2d88ebb0bb27539f897:25 (anonymous) @
main.js:1

Answer 1

Angular 4.3 introduced a new module, HttpClientModule, which is a complete rewrite of the existing HttpModule.

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

to:

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

The second step is to replace every instance of the service Http with the new service HttpClient.

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

@Injectable()
export class UserService {

  constructor(private http: HttpClient) {}

  list(): Observable<UserModel> {
    return this.http.get('/api/users');
  }
}

Answer 2

Вы используете модуль HttpClient вместо HttpClientModule.Поэтому замените HttpClient на HttpCLientModule в обоих импортах как

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

и

  imports: [
    BrowserModule,
    HttpClientModule, 
    IonicModule.forRoot(MyApp)
  ]

Answer 3

Вы должны import модуль HttpClientModule и ссылаться на него в импорте.

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

  imports: [
    BrowserModule,
    HttpClientModule, // import the module
    IonicModule.forRoot(MyApp)
  ]