@Directive({
 selector: 'p'
})
export class TodoDirective{
 constructor(el: ElementRef, renderer: Renderer){
  renderer.setElementStyle(el.nativeElement, 'backgroundColor', 'red');
 }
}

//模板内容
<p *ngFor='let item of todos' #name>{{ item.name }}</p>

//组件中获取DOM
@ViewChildren('name')
todoNames: QueryList<ElementRef>;

@ViewChild('name')
todoName: ElementRef;
ngAfterViewInit(){
 this.todoNames.forEach(e=>console.log(e.nativeElement.innerText));
 console.log(this.todoName.nativeElement.innerText);
}

this.todoNames.changes.subscribe(data => data._results.forEach(
 e=>console.log(e.nativeElement.innerText)));
this.todoNames.notifyOnChanges();

import {Component, ContentChildren, Directive, Input, QueryList} from '@angular/core';
@Directive({selector: 'pane'})
export class Pane {
 @Input() id: string;
}
@Component({
 selector: 'tab',
 template: `
 <div>panes: {{serializedPanes}}</div> 
 `
})
export class Tab {
 @ContentChildren(Pane) panes: QueryList<Pane>;
 get serializedPanes(): string { return this.panes ? this.panes.map(p => p.id).join(', ') : ''; }
}
@Component({
 selector: 'example-app',
 template: `
 <tab>
  <pane id="1"></pane>
  <pane id="2"></pane>
  <pane id="3" *ngIf="shouldShow"></pane>
 </tab>
 <button (click)="show()">Show 3</button>
 `,
})
export class ContentChildrenComp {
 shouldShow = false;
 show() { this.shouldShow = true; }
}

 <tab>
  <pane id="1"></pane>
  <pane id="2"></pane>
  <pane id="3" *ngIf="shouldShow"></pane>
 </tab>