interface
A lifecycle hook that is called when any data-bound property of a directive changes. Define an ngOnChanges()
method to handle the changes.
interface OnChanges { ngOnChanges(changes: SimpleChanges): void }
ngOnChanges() | |||
---|---|---|---|
A callback method that is invoked immediately after the default change detector has checked data-bound properties if at least one has changed, and before the view and content children are checked. | |||
|
changes | SimpleChanges | The changed properties. |
void
The following snippet shows how a component can implement this interface to define an on-changes handler for an input property.
@Component({selector: 'my-cmp', template: `...`}) class MyComponent implements OnChanges { @Input() prop: number = 0; ngOnChanges(changes: SimpleChanges) { // changes.prop contains the old and the new value... } }
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https://v12.angular.io/api/core/OnChanges