![如何访问父组件上定义的]( "如何访问父组件上定义的")
本文介绍了如何访问父组件上定义的 ViewChild 引用 - Angular 2的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我在应用程序模板(根组件的模板)中定义了一个微调器/加载器元素，例如
<!--我把它放在这里，这样我就不必将它粘贴到我所有的模板中--><div #spinner></div>
在我的子组件中，我尝试使用 @ViewChild 访问它，但这似乎总是返回 undefined.我在子组件中访问它的代码是
@ViewChild('spinner', { read: ViewContainerRef }) 容器:ViewContainerRef;//这总是未定义的
但是，当我将 #spinner 放在子组件的 HTML 中时，它会被正确拾取.
有没有办法将子组件中父组件中定义的元素作为 ContainerRef 获取?
我需要视图引用以使用 ComponentFactoryResolver 在其上动态创建组件.
这似乎是一个类似的问题，但找不到克服的方法.
我现在使用可观察的共享服务，但它仍然没有在 .next 上引发事件.
这是我在 SpinnerComponent
中的代码@Component({选择器:'微调器'，styleUrls: ['app/styles/spinner.component.css'],模板:`<div [hidden]="state.visible" class="in modal-backdrop spinner-overlay"></div><div class="spinner-message-container" aria-live="assertive" aria-atomic="true"><div class="spinner-message" [ngClass]="spinnerMessageClass">{{ state.message }}</div>
`})导出类 SpinnerComponent {构造函数(微调服务:微调服务){spinnerService.spinnerStatus.subscribe(event => {console.log('事件:' + 事件);<= 没有被调用this.state.visible = 事件；});}公共状态 = {message: '请稍候...',可见:假};}
在 SpinnerService 中，我有
@Injectable()导出类 SpinnerService {公共事件:BehaviorSubject= new BehaviorSubject(false);public get spinnerStatus(): Observable{返回 this.events.asObservable();}公共 showSpinner() {this.events.next(true);}公共隐藏旋转器(){this.events.next(false);}}
在调用组件中，我有
@Component({选择器:'编辑拍卖'，templateUrl: '/auctions/edit.html'})导出类 EditAuctionComponent {构造函数(公共微调服务:SpinnerService){}ngAfterViewInit() {//启动微调器this.spinnerService.showSpinner();}}
在 app.module.ts(根模块)中
@NgModule({进口:[BrowserModule，FormsModule，HttpModule，路线]，声明:[..]，提供者:[NotificationsService，SpinnerService]，引导程序:[AppComponent]})导出类 AppModule { }
解决方案
从其他组件访问数据对我来说听起来不太好.
对于您尝试做的最好的事情可能是定义将共享可观察的服务:
@Injectable()导出类 EventService {public selectedCategoryName: string = '';私人事件 = 新的 BehaviorSubject(false);构造函数(){}公共 showSpinner(){this.events.next(真)}公共隐藏旋转器(){this.events.next(false);}public get spinnerStatus() : Observable{返回 this.events.asObservable();}}
然后在你的根组件中订阅
eventServiceInstance.spinnerStatus.subscribe(state=>{//thisSpinner.visible = state})
现在你会在所有其他地方打电话
eventServiceInstance.showSpinner()eventServiceInstance.hideSpinner()
附注.为了使其工作，EventService 提供者应该添加到 NgModule 中，而不是在组件内部
I have a spinner/loader element defined in app template (root component's template) like
<!--I have it here so that I don't have to paste it in all my templates-->
<div #spinner></div>
In my child components, I am trying to access it using @ViewChild but that seems to always return undefined. My code for accessing this in child component is
@ViewChild('spinner', { read: ViewContainerRef }) container: ViewContainerRef; //this is always undefined
However when I place my #spinner in my child component's HTML, it gets picked up correctly.
Is there a way to get the element defined in parent component in your child component as a ContainerRef?
I need the view reference to create the component on it dynamically using ComponentFactoryResolver.
It seems a similar issue but can't find a way to overcome.
EDIT: I am now using a shared service with the observable, but still it doesn't raise an event on .next.
Here is my code in SpinnerComponent
@Component({
selector: 'spinner',
styleUrls: ['app/styles/spinner.component.css'],
template:
`<div [hidden]="state.visible" class="in modal-backdrop spinner-overlay"></div>
<div class="spinner-message-container" aria-live="assertive" aria-atomic="true">
<div class="spinner-message" [ngClass]="spinnerMessageClass">{{ state.message }}</div>
</div>`
})
export class SpinnerComponent {
constructor(spinnerService: SpinnerService) {
spinnerService.spinnerStatus.subscribe(event => {
console.log('Event: ' + event); <= not getting called
this.state.visible = event;
});
}
public state = {
message: 'Please wait...',
visible: false
};
}
In SpinnerService, I have
@Injectable()
export class SpinnerService {
public events: BehaviorSubject<boolean> = new BehaviorSubject<boolean>(false);
public get spinnerStatus(): Observable<boolean> {
return this.events.asObservable();
}
public showSpinner() {
this.events.next(true);
}
public hideSpinner() {
this.events.next(false);
}
}
And in the calling component, I have
@Component({
selector: 'edit-auction',
templateUrl: '/auctions/edit.html'
})
export class EditAuctionComponent {
constructor(public spinnerService: SpinnerService) { }
ngAfterViewInit() {
//start the spinner
this.spinnerService.showSpinner();
}
}
In app.module.ts (root module)
@NgModule({
imports: [BrowserModule, FormsModule, HttpModule, routes],
declarations: [..],
providers: [NotificationsService, SpinnerService],
bootstrap: [AppComponent]
})
export class AppModule { }
解决方案
Accessing data from other components does not sounds good to me.
For what you are trying to do probably best would be to define service which will share observable:
@Injectable()
export class EventService {
public selectedCategoryName: string = '';
private events = new BehaviorSubject<Boolean>(false);
constructor() {
}
public showSpinner(){
this.events.next(true)
}
public hideSpinner(){
this.events.next(false);
}
public get spinnerStatus() : Observable<boolean> {
return this.events.asObservable();
}
}
Then in your root component you will subscribe to
eventServiceInstance.spinnerStatus.subscribe(state=>{
//thisSpinner.visible = state
})
And now in all other places you will call
eventServiceInstance.showSpinner()
eventServiceInstance.hideSpinner()
PS. To make it works EventService provider should be added in NgModule and not inside of components
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