Angular2：ViewChild

<!DOCTYPE html>
<html>

  <head>
    <title>angular2 playground</title>
    <link rel="stylesheet" href="style.css" />
    <script src="https://code.angularjs.org/tools/system.js"></script>
    <script src="https://code.angularjs.org/tools/typescript.js"></script>
    <script src="config.js"></script>
    <script src="https://code.angularjs.org/2.0.0-beta.0/angular2-polyfills.min.js"></script>
    <script src="https://code.angularjs.org/2.0.0-beta.0/Rx.min.js"></script>
    <script src="https://code.angularjs.org/2.0.0-beta.0/angular2.min.js"></script>
    <script src="https://code.angularjs.org/2.0.0-beta.0/http.min.js"></script>
    <script src="https://code.angularjs.org/2.0.0-beta.0/router.min.js"></script>
    <script>
    System.import('app')
      .catch(console.error.bind(console));
  </script>
  </head>

  <body>
    <my-app>
      Loading...
    </my-app>
  </body>

</html>

/* Styles go here */

System.config({
  //use typescript for compilation
  transpiler: 'typescript',
  //typescript compiler options
  typescriptOptions: {
    emitDecoratorMetadata: true
  },
  //map tells the System loader where to look for things
  map: {
    app: "./src"  },
  //packages defines our app package
  packages: {
    app: {
      main: './app.ts',
      defaultExtension: 'ts'
    }
  }
});

//our root app component
import {Component} from 'angular2/core';
import {bootstrap} from 'angular2/platform/browser';
import {ParentComponent}   from './parent.ts';
import {ChildComponent}    from './child.ts';

@Component({
    selector: 'my-app',
    template: `
        <h2>App Component</h2>
        <my-parent></my-parent>
    `,
    directives:[ParentComponent,ChildComponent]
})
export class AppComponent {
}

bootstrap(AppComponent).catch(err => console.error(err));

import {Component,ViewChild,AfterViewInit} from 'angular2/core';
import {ChildComponent}         from './child';

@Component({
    selector: 'my-parent',
    template: `
       <div>Parent Component</div>
       <my-child></my-child>
    `,
    directives:[ChildComponent]
})
export class ParentComponent implements AfterViewInit{
    @ViewChild(ChildComponent)
    child:ChildComponent;

    ngAfterViewInit() {
        console.log(this.child)
    }
}

import {Component} from 'angular2/core';

@Component({
    selector: 'my-child',
    template: `
        <div>Child Component</div>
    `
})
export class ChildComponent {
    name:string = 'childName';
}