OnChanges
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
}
See also
Lifecycle Hooks guide
Methods
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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. |
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Parameters
Returns
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Usage notes
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 {
// TODO(issue/24571): remove '!'.
@Input()
prop !: number;
ngOnChanges(changes: SimpleChanges) {
// changes.prop contains the old and the new value...
}
}