Question

https://stackoverflow.com/questions/50935728/access-viewchild-from-another-component

=================

I have two components, one videoComponent and videoControlsComponent. The video component contains a <video> element and the video component has some buttons to manipulate the videoComponent <video> element.

<video controls="{{ controls }}" [src]="streamUrl" #myVideo>
    Your browser does not support the video tag or the file format of this video.
</video>

videoComponent:

@ViewChild('myVideo') myVideo: any;
public playVideo() {
    this.myVideo.nativeElement.play();
}

videoControlComponent:

constructor(private videoComponent: VideoComponent) { }
public videoPlay() {
    this.videoComponent.playVideo()
}

The problem is that when I click the button I get the following error: Cannot read property 'nativeElement' of undefined at VideoControlsComponent.

But when I have exactly the same code but create the button not in the videoControlsComponent but videoComponent everything works fine.

Can you help me out please?

Answer 1

you need to use @ViewChild like you did with "myVideo" with videoComponent as well so like this @ViewChild(VideoComponent) videoComponent: VideoComponent

that's assuming videoComponent is a child of videoControls

if they are siblings you can use @Output to trigger an event in the parent, the parent would then change a boolean that is set to an input in videoControls and then set up ngOnChanges on videoControls to detect when that input changes

or you can set up a service to communicate between them. That might be the easiest option if they are not a parent-child relationship

Example of a Service to communicate between components:

@Injectable()
export class MyService {
    private myFunctionCallSource = new Subject();

    myFunctionCalled$ = this.myFunctionCallSource.asObservable();

    callMyFunction(){
        this.myFunctionCallSource.next()
    }
}

in videoComponent

this.myService.myFunctionCalled$.subscribe(
    res => this.myVideo.nativeElement.play(),
    err => console.log('MyService error', err)
);

in videoControlsComponent

this.myService.callMyFucnction()