Angular Material get previously selected value from MatSelectChange event

user_8384588 0
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I am capturing MatSelectChange events from a dynamic forms library in my .ts file. This works just fine, but when I capture the event, I don't know how to acquire the previously selected value.

Getting the current value is easy, I am surprised that the prior value isn't immediately available for access.

The event contains access to $event.value and $event.source.

I have tried to dig deep into the source member, but I can't find the previous value there either as it is just the current select control.

Link to API

angular-forms angular-material angular
1 Answers

There is no way to get it from the event unfortunately. You will have to store it in a component variable, and read it from there. Which shouldn't add that much overhead, because most of the time you would have to do that anyways:

export class SelectOverviewExample {
  selected?: string;

  onChange(event: MatSelectChange): void {
    console.log('Old value', this.selected);
    this.selected = event.value;
    console.log('New value', event.value);
  }
}

stackblitz

user_31069200
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