I have an @Input that does something when it's true ngOnChange doesn't detect when it's false

```
@Input() viewMode: boolean;

  ngOnChanges(changes: SimpleChanges) {
    if (changes.viewMode.currentValue !== undefined) {    
      if (changes.viewMode.currentValue ) {
        this.populateForm(this._event);
      }else{
        this.doSomething()
      }
    }
  }

setValue(){

   this.viewMode = false; 
}

```

When I call the setValue function it doesn't fall into ngOnChange