Suppose i have simple Bootstrap panel component with multiple transclusion slots. Template example:
<div class="panel panel-default">
<div class="panel-heading">
<ng-content select="my-panel-heading"></ng-content>
</div>
<div class="panel-body">
<ng-content select="my-panel-content"></ng-content>
</div>
</div>
I want to make panel-heading optional. How do i hide <div class="panel-heading">
element, if there is no content provided for <ng-content select="my-panel-heading"></ng-content>
If you have a parent element of <ng-content>
with a template variable (#panelHeading
)
<div class="panel panel-default">
<div class="panel-heading" #panelHeading [hidden]="!showHeading">
<ng-content select="my-panel-heading"></ng-content>
</div>
<div class="panel-body">
<ng-content select="my-panel-content"></ng-content>
</div>
</div>
then you can query for it like
@ViewChild('panelHeading') panelHeading;
and set a property depending on whether there are children or not
constructor(private cdRef:ChangeDetectorRef) {}
showHeading:boolean = false;
ngAfterViewInit() {
this.showHeading = this.panelHeading.nativeElement && this.panelHeading.nativeElement.children.length > 0;
this.cdRef.detectChanges();
}
If <my-panel-heading>
is an Angular2 component, then you can also use
@ContentChild(MyPanelHeading) panelHeading:MyPanelHeading;
constructor(private cdRef:ChangeDetectorRef) {}
showHeading:boolean = false;
ngAfterViewInit() {
this.showHeading = this.panelHeading != null;
this.cdRef.detectChanges();
}