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The Flutter GetX Ecosystem

The ValueBuilder and ObxValue Widgets

Learn to handle a widget’s local state with ValueBuilder and ObxValue.

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Introduction

ValueBuilder and ObxValue are stateful widgets that control the local state of the widget they wrap around. Consider we have a switch; we can control its toggle state simply by wrapping it with one of these widgets. There is no need to create a variable or a toggle method with setState. This helps us classify the code for widgets whose state can be defined by a single variable.

ValueBuilder

ValueBuilder is a local state manager that defines a widget’s state using a single variable and provides the mechanism to update it. If the variable’s value changes, it updates the state and rebuilds the widget.

Let’s look at its syntax:

Dart
ValueBuilder<bool?>(
  initialValue: false,
  builder: (snapshot, updater) => Switch(value: snapshot!, onChanged: updater),
)

ValueBuilder takes the type of the value and has the initialValue parameter, where we specify the initial value to be used. builder is a function with two parameters—snapshot and updater. snapshot is the latest snapshot of the value, and updater is the function responsible for rebuilding the widget. ...