单页面应用组件通信有以下几种，这篇文章主要讲 Angular 通信

1. 父组件 => 子组件

2. 子组件 => 父组件

3. 组件A = > 组件B

上面图表总结了能用到通信方案,期中最后3种,是通用的,angular的组件之间都可以使用这3种,其中Rxjs是最最牛逼的用法,甩redux,promise,这些同样基于函数式的状态管理几条街,下面一一说来

父组件 => 子组件

@input,最常用的一种方式

@Component({
 selector: 'app-parent',
template: '<p>childText:<app-child [textContent] = "varString"></app-child></p>',
 styleUrls: ['./parent.component.css']
})
export class ParentComponent implements OnInit {
 varString: string;
 constructor() { }
 ngOnInit() {
 this.varString = '从父组件传过来的' ;
 }
}

import { Component, OnInit, Input } from '@angular/core';
@Component({
 selector: 'app-child',
 template: '<h1>{{textContent}}</h1>',
 styleUrls: ['./child.component.css']
})
export class ChildComponent implements OnInit {
 @Input() public textContent: string ;
 constructor() { }
 ngOnInit() {
 }
}

setter

setter 是拦截@input 属性,因为我们在组件通信的时候,常常需要对输入的属性处理下,就需要setter了,setter和getter常配套使用,稍微修改下上面的child.component.ts
child.component.ts

import { Component, OnInit, Input } from '@angular/core';
@Component({
 selector: 'app-child',
 template: '<h1>{{textContent}}</h1>',
 styleUrls: ['./child.component.css']
})
export class ChildComponent implements OnInit {
_textContent:string;
 @Input()
 set textContent(text: string){
 this._textContent = !text: "啥都没有给我" ? text ;
 } ;
 get textContent(){
 return this._textContent;
 }
 constructor() { }
 ngOnInit() {
 }
}

onChange

这个是通过angular生命周期钩子来检测,不推荐使用,要使用的话可以参angular文档

@ViewChild()

@ViewChild() 一般用在调用子组件非私有的方法

 import {Component, OnInit, ViewChild} from '@angular/core';
 import {ViewChildChildComponent} from "../view-child-child/view-child-child.component";
 @Component({
 selector: 'app-parent',
 templateUrl: './parent.component.html',
 styleUrls: ['./parent.component.css']
 })
 export class ParentComponent implements OnInit {
 varString: string;
 @ViewChild(ViewChildChildComponent)
 viewChildChildComponent: ViewChildChildComponent;
 constructor() { }
 ngOnInit() {
 this.varString = '从父组件传过来的' ;
 }
 clickEvent(clickEvent: any) {
 console.log(clickEvent);
 this.viewChildChildComponent.myName(clickEvent.value);
 }
 }

 import { Component, OnInit } from '@angular/core';
 @Component({
 selector: 'app-view-child-child',
 templateUrl: './view-child-child.component.html',
 styleUrls: ['./view-child-child.component.css']
 })
 export class ViewChildChildComponent implements OnInit {
 constructor() { }
 name: string;
 myName(name: string) {
 console.log(name);
 this.name = name ;
 }
 ngOnInit() {
 }
 }

局部变量

局部变量和viewChild类似,只能用在html模板里,修改parent.component.html,通过#viewChild这个变量来表示子组件,就能调用子组件的方法了.

<p class="panel-body">
 <input class="form-control" type="text" #viewChildInputName >
 <button class=" btn btn-primary" (click)="viewChild.myName(viewChildInputName.value)">局部变量传值</button>
 <app-view-child-child #viewChild></app-view-child-child>
 </p>

child 组件如下

@Component({
 selector: 'app-view-child-child',
 templateUrl: './view-child-child.component.html',
 styleUrls: ['./view-child-child.component.css']
})
export class ViewChildChildComponent implements OnInit {

 constructor() { }
 name: string;
 myName(name: string) {
 console.log(name);
 this.name = name ;
 }
 ngOnInit() {
 }

}

子组件 => 父组件

@output()

output这种常见的通信,本质是给子组件传入一个function,在子组件里执行完某些方法后,再执行传入的这个回调function,将值传给父组件

parent.component.ts
@Component({
 selector: 'app-child-to-parent',
 templateUrl: './parent.component.html',
 styleUrls: ['./parent.component.css']
})
export class ChildToParentComponent implements OnInit {

 childName: string;
 childNameForInject: string;
 constructor( ) { }
 ngOnInit() {
 }
 showChildName(name: string) {
 this.childName = name;
 }
}

parent.component.html

<p class="panel-body">
 <p>output方式 childText:{{childName}}</p>
 <br>
 <app-output-child (childNameEventEmitter)="showChildName($event)"></app-output-child>
</p>

 child.component.ts
 export class OutputChildComponent implements OnInit {
 // 传入的回调事件
 @Output() public childNameEventEmitter: EventEmitter<any> = new EventEmitter();
 constructor() { }
 ngOnInit() {
 }
 showMyName(value) {
 //这里就执行,父组件传入的函数
 this.childNameEventEmitter.emit(value);
 }
}

注入父组件

这个原理的原因是父,子组件本质生命周期是一样的

export class OutputChildComponent implements OnInit {
 // 注入父组件
 constructor(private childToParentComponent: ChildToParentComponent) { }
 ngOnInit() {
 }
 showMyName(value) {
 this.childToParentComponent.childNameForInject = value;
 }
}

sibling组件 => sibling组件

service

Rxjs

通过service通信

angular中service是单例的,所以三种通信类型都可以通过service,很多前端对单例理解的不是很清楚,本质就是
,你在某个module中注入service,所有这个modul的component都可以拿到这个service的属性,方法,是共享的,所以常在app.moudule.ts注入日志service,http拦截service,在子module注入的service,只能这个子module能共享,在component注入的service,就只能子的component的能拿到service,下面以注入到app.module.ts,的service来演示

user.service.ts
@Injectable()
export class UserService {
 age: number;
 userName: string;
 constructor() { }
}
app.module.ts
@NgModule({
 declarations: [
 AppComponent,
 SiblingAComponent,
 SiblingBComponent
 ],
 imports: [
 BrowserModule
 ],
 providers: [UserService],
 bootstrap: [AppComponent]
})
export class AppModule { }
SiblingBComponent.ts
@Component({
 selector: 'app-sibling-b',
 templateUrl: './sibling-b.component.html',
 styleUrls: ['./sibling-b.component.css']
})
export class SiblingBComponent implements OnInit {
 constructor(private userService: UserService) {
 this.userService.userName = "王二";
 }
 ngOnInit() {
 }
}
SiblingAComponent.ts
@Component({
 selector: 'app-sibling-a',
 templateUrl: './sibling-a.component.html',
 styleUrls: ['./sibling-a.component.css']
})
export class SiblingAComponent implements OnInit {
 userName: string;
 constructor(private userService: UserService) {
 }
 ngOnInit() {
 this.userName = this.userService.userName;
 }
}

通过Rx.js通信

这个是最牛逼的,基于订阅发布的这种流文件处理,一旦订阅,发布的源头发生改变,订阅者就能拿到这个变化;这样说不是很好理解,简单解释就是,b.js,c.js,d.js订阅了a.js里某个值变化,b.js,c.js,d.js立马获取到这个变化的,但是a.js并没有主动调用b.js,c.js,d.js这些里面的方法,举个简单的例子,每个页面在处理ajax请求的时候,都有一弹出的提示信息,一般我会在
组件的template中中放一个提示框的组件,这样很繁琐每个组件都要来一次,如果基于Rx.js,就可以在app.component.ts中放这个提示组件,然后app.component.ts订阅公共的service,就比较省事了,代码如下
首先搞一个alset.service.ts

import {Injectable} from "@angular/core";
import {Subject} from "rxjs/Subject";
@Injectable()
export class AlertService {
 private messageSu = new Subject<string>(); //
 messageObserve = this.messageSu.asObservable();
 private setMessage(message: string) {
 this.messageSu.next(message);
 }
 public success(message: string, callback?: Function) {
 this.setMessage(message);
 callback();
 }
}

sibling-a.component.ts

@Component({
 selector: 'app-sibling-a',
 templateUrl: './sibling-a.component.html',
 styleUrls: ['./sibling-a.component.css']
})
export class SiblingAComponent implements OnInit {
 userName: string;
 constructor(private userService: UserService, private alertService: AlertService) {
 }
 ngOnInit() {
 this.userName = this.userService.userName;
 // 改变alertService的信息源
 this.alertService.success("初始化成功");
 }
}

app.component.ts

@Component({
 selector: 'app-root',
 templateUrl: './app.component.html',
 styleUrls: ['./app.component.css']
})
export class AppComponent {
 title = 'app';
 message: string;
 constructor(private alertService: AlertService) {
 //订阅alertServcie的message服务
 this.alertService.messageObserve.subscribe((res: any) => {
 this.message = res;
 });
 }
}

这样订阅者就能动态的跟着发布源变化

总结: