Problem Statement
What is ValueNotifier and when should you use it?
Explanation
ValueNotifier is a special type of ChangeNotifier that holds a single value and automatically calls notifyListeners() when you assign a new value. It's perfect for simple reactive state where you don't need a full model class - just wrap a value in ValueNotifier and use ValueListenableBuilder to rebuild widgets when the value changes.
ValueNotifier eliminates boilerplate for simple state management - you don't need to create a class, extend ChangeNotifier, or remember to call notifyListeners(). Just create ValueNotifier<int>(0) and assign new values with valueNotifier.value = newValue. The notification happens automatically, making it ideal for counters, toggles, simple form fields, or any single-value state.
Use ValueNotifier with ValueListenableBuilder which rebuilds only when the value changes, providing fine-grained rebuild control without Provider. It's more lightweight than ChangeNotifier for simple cases but less suitable for complex state with multiple properties. Choose ValueNotifier for simple reactive values, ChangeNotifier for complex models with multiple properties.
