functional_listener library Null safety


Sometimes you want a ValueNotifier where you can control when its listeners are notified. With the CustomValueNotifier you can do this: If you pass CustomNotifierMode.always for the mode parameter, notifierListeners will be called everytime you assign a value to the value property independent of if the value is different from the previous one. If you pass CustomNotifierMode.manual for the mode parameter, notifierListeners will not be called when you assign a value to the value property. You have to call it manually to notify the Listeners.
Object that is returned by listen that allows you to stop the calling of the handler that you passed to it.


extension functions on ValueListenable that allows you to work with them almost as if it was a synchronous stream. Each extension function returns a new ValueNotifier that updates its value when the value of this changes You can chain these functions to build complex processing pipelines from a simple ValueListenable In the examples we use listen to react on value changes. Instead of applying listen you could also pass the end of the function chain to a ValueListenableBuilder