// @Component装饰器标识这是一个组件
@Component({
  //selector: 'app-article',
  //selector: '[app-article]', //属性方式
  selector: '.app-article', //类方式
  templateUrl: './article.component.html',
  styleUrls: ['./article.component.css']
})

import { DatePipe } from '@angular/common';

constructor(private datePipe: DatePipe) {}

this.datePipe.transform()

@Pipe({
  name: "flyingHeroesImpure",
  pure: false,
})
export class FlyingHeroesImpurePipe extends FlyingHeroesPipe {}

import { BrowserModule } from "@angular/platform-browser";
import { NgModule } from "@angular/core";

import { AppRoutingModule } from "./app-routing.module";
import { AppComponent } from "./app.component";

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, AppRoutingModule],
  providers: [],
  bootstrap: [AppComponent],
})
export class AppModule {}

// 输入
<child title = "我的子组件"> </child>
@Input
public title: string = "";
// 输出
<child title="我的子组件" (follow)="getFollow($event)" #child ></child>

@Output()
public follow = new EventEmitter();
this.follow.emit("子组件传来的数据");

import {
  Injectable
} from "@angular/core";
import {
  Observable,
  Subject
} from "rxjs";

// 服务总线 组件间分享数据
@Injectable({
  providedIn: "root" // 在所有组件共享数据
})
export class EventBusService {
  public eventBus: Subject < string > = new Subject();
  constructor() {}
}

import { Injectable } from "@angular/core";
import { UserModule } from "./user.module";

@Injectable({
  providedIn: UserModule,
})
export class UserService {}

import { NgModule } from "@angular/core";
import { Routes, RouterModule } from "@angular/router";
import { ChildComponent } from "./child/child.component";
import { BrotherComponent } from "./brother/brother.component";

const routes: Routes = [
  {
    path: "",
    component: ChildComponent,
  },
  {
    path: "brother",
    component: BrotherComponent,
  },
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule],
})
export class AppRoutingModule {}

const routes: Routes = [
  {
    path: "items",
    loadChildren: () => import("./items/items.module").then((m) => m.ItemsModule),
  },
];

// app.module.ts
import { HttpModule } from "@angular/http";
import { HttpClientModule } from "@angular/common/http";
// services
import { Headers } from "@angular/http";
import { HttpClient, HttpResponse } from "@angular/common/http";

this.httpClient.request(UserService.METHOD_POST, url, options).subscribe(
  (next) => {},
  (error) => {},
  (complete) => {} // 指next完成后，会执行complete, 并不是finally的意思
);

this.httpClient.request(UserService.METHOD_POST, url, options).toPromise();

class MyErrorHandler implements ErrorHandler {
  handleError(error) {
    // do something with the exception
  }
}

@NgModule({
  providers: [{ provide: ErrorHandler, useClass: MyErrorHandler }],
})
class MyModule {}