了解Angular2---App的生命周期

摘要: 一个app的运行有多个阶段,我们可以在app开始.运行.和创建/终止组件的时候添加响应

bootstrap

Angular2中,一个App需要用它的根组件进行引导

import {Component, bootstrap} from 'angular2/angular2';

// Annotation section
@Component({
selector: 'my-app',
template: '<h1>Hello {{ name }}</h1>'
})
// Component controllerclass MyApp {
constructor() {
this.name = 'Max';
}
}

bootstrap(MyApp)

你可以把应用程序的代码和配置文件放到这个组件中,并且整个应用程序的组件链将会在它的模板文件中被创建

初始化组件

当一个组件被创建的时候,它的构造器就会生效.我们就是在这个构造器里面初始化组件的状态.但是如果要用到子组件当中的属性或者数据的话,就需要先等待一段时间.(等父组件依赖的子组件被创建之后才能初始化父组件).

这种情况下,我们可以使用setTimeout来解决这个问题.但是在这里,我们推荐你用生命周期事件onInit:

import {Component, bootstrap, onInit} from 'angular2/angular2';

// Annotation section
@Component({
selector: 'street-map',
template: '<map-window></map-window><map-controls></map-controls>',
lifecycle: [onInit]
})

// Component controller
class StreetMap {
constructor() {
this.name = 'Max';

setTimeout(() => {
// Similar to onInit below, but not recommended.
// Could be useful in a pinch, though.
});
}

setMapWindow(mapWindow) {
this.mapWindow = mapWindow;
}

setMapControls(mapControls) {
this.mapControls = mapControls;
}

onInit() {
// Properties are resolved and things like
// this.mapWindow and this.mapControls
// had a chance to resolve from the
// two child components <map-window> and <map-controls>
}}

组件的生命周期

就像onInit,我们可以根据组件的生命周期追踪几个事件

import {..., onInit, onDestroy, onChange, onCheck, onAllChangesDone} from 'angular2/angular2';
// Annotation section
@Component({
selector: 'street-map',
template: '<map-window></map-window><map-controls></map-controls>',
lifecycle: [onInit, onDestroy, onChange, onCheck, onAllChangesDone]
})
// Component controller
class StreetMap {
onInit() {
// Properties are resolved and things like
// this.mapWindow and this.mapControls
// had a chance to resolve from the
// two child components <map-window> and <map-controls>
}
onDestroy() {
// Speak now or forever hold your peace
}
onCheck() {
// Called right after our bindings have been checked
}
onChange(changes) {
// Called right after our bindings have been checked but only
// if one of our bindings has changed.
//
// changes is an object of the format:
// {
//   'prop': PropertyUpdate
// }
}
onAllChangesDone() {
// Called right after all of our bindings have been checked
}}

原文链接