How to add "class" to host element?
I dont't know how to add to my component <component></component> a dynamic class attribute but inside the template html (component.html).
The only solution I found is to modify the item via "ElementRef" native element. That solution seems a little complicated to do something that should be very simple.
Another problem is that CSS has to be defined outside component scope, breaking component encapsulation.
Is there a simpler solution? Something like <root [class]="..."> .... </ root> inside the template.
Solution 1:
This way you don't need to add the CSS outside of the component:
@Component({
selector: 'body',
template: 'app-element',
// prefer decorators (see below)
// host: {'[class.someClass]':'someField'}
})
export class App implements OnInit {
constructor(private cdRef:ChangeDetectorRef) {}
someField: boolean = false;
// alternatively also the host parameter in the @Component()` decorator can be used
@HostBinding('class.someClass') someField: boolean = false;
ngOnInit() {
this.someField = true; // set class `someClass` on `<body>`
//this.cdRef.detectChanges();
}
}
Plunker example
This CSS is defined inside the component and the selector is only applied if the class someClass is set on the host element (from outside):
:host(.someClass) {
background-color: red;
}
Solution 2:
Günter's answer is great (question is asking for dynamic class attribute) but I thought I would add just for completeness...
If you're looking for a quick and clean way to add one or more static classes to the host element of your component (i.e., for theme-styling purposes) you can just do:
@Component({
selector: 'my-component',
template: 'app-element',
host: {'class': 'someClass1'}
})
export class App implements OnInit {
...
}
And if you use a class on the entry tag, Angular will merge the classes, i.e.,
<my-component class="someClass2">
I have both someClass1 & someClass2 applied to me
</my-component>
Solution 3:
You can simply add @HostBinding('class') class = 'someClass'; inside your @Component class.
Example:
@Component({
selector: 'body',
template: 'app-element'
})
export class App implements OnInit {
@HostBinding('class') class = 'someClass';
constructor() {}
ngOnInit() {}
}