Angular Version: 6.1
I\'m trying to implement a custom control using what Kara Erickson is calling a Composite ControlValueAccessor as shown in the presentation, An
The purpose of writeValue is to inform your component about changes on the outside / the form control on parent component. What you'll usually want to do with it is to bind the change from outside to a local variable.
In order to inform the outside world about changes inside of your component, you need to call the onChange method. You can call it, like you would usually call an event emitter.
I've put together a couple of examples here: https://www.tsmean.com/articles/angular/angular-control-value-accessor-example/