Angular2学习教程之ng中变更检测问题详解

@Component({
 selector: 'todo-list',
 template: `
  <p *ngFor='let item of todos'>{{ item.name }}</p>
 `,
})
export class TodoComponent{
 @Input() todos: Todo[];

 public getTodos():Todo[]{
  return this.todos;
 }
}

@Component({
 selector: 'app-todo-data',
 template: `<p *ngFor='let item of todos'>{{ item.name }}</p>
  <button (click)='getData()'>get data</button>`,
 styleUrls: ['./todo-data.component.css'],
 inputs: ['todoComponent'],
})
export class TodoDataComponent implements OnInit {
 todoComponent: TodoComponent;
 todos: Todo[]
 constructor() { }
 ngOnInit() {
 }
 getData(){
  this.todos=this.todoComponent.getTodos();
 }
}

//app.component.htm
<div>
 <div *ngIf='loading'>
  <todo-list [todos]='todos'></todo-list>
  <button (click)='changeall()'>next</button>
 </div>
</div>
<div>
 <app-todo-data [todoComponent]='todoComponent'></app-todo-data>
</div>

//app.component.ts
@Component({
 selector: 'app-root',
 templateUrl: './app.component.html',
 styleUrls: ['./app.component.css'],
})
export class AppComponent implements OnInit {
 todos: Todo[];
 @ViewChild(TodoComponent)
 todoComponent: TodoComponent;
 loading: boolean = true;
 constructor(private todoService:TodoService){
  super(true);
 }
 ngOnInit(){
  this.todoService.todos.subscribe(data => {this.todos=data});
  this.todoService.load(0, 3);
 }
 changeall(){
  this.todoService.load(3, 3);
 }
}

constructor(private todoService:TodoService, private cdr: ChangeDetectorRef){}

ngAfterViewInit(){
 this.cdr.detectChanges();
}

setInterval(() => {
this.numberOfTicks ++
 // the following is required, otherwise the view will not be updated
 this.ref.markForCheck();
}, 1000);

ref.detach();
setInterval(() => {
 this.ref.detectChanges();
}, 5000);

@Component({
 selector: 'todo-list',
 changeDetection: ChangeDetectionStrategy.OnPush,
})