angular 组件通信的几种实现方式

2019-11-19 13:30:08

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单页面应用组件通信有以下几种，这篇文章主要讲 Angular 通信

父组件 => 子组件
子组件 => 父组件
组件A = > 组件B

父组件 => 子组件	子组件 => 父组件	sibling => sibling
@input	@output
setters (本质上还是@input)	注入父组件
ngOnChanges() (不推荐使用)
局部变量
@ViewChild()
service	service	service
Rxjs的Observalbe	Rxjs的Observalbe	Rxjs的Observalbe
localStorage,sessionStorage	localStorage,sessionStorage	localStorage,sessionStorage

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: '<div>childText:<app-child [textContent] = "varString"></app-child></div>', 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.

<div 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>      </div>

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

<div class="panel-body"> <p>output方式 childText:{{childName}}</p> <br> <app-output-child (childNameEventEmitter)="showChildName($event)"></app-output-child></div> 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: 以上就是常用的的通信方式,各种场景可以采取不同的方法。希望对大家的学习有所帮助，也希望大家多多支持武林网。

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