Question 79766 in Flutter Question posted in
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How to use GetxController inside my view without removing the const keyword on the constructor – Flutter

using Getx, when I have a GetxController and I want to use it inside my view UI, it required removing const on the widget constructor :

Controller :

class TestController extends GetxController {
// ...
}

View :

 class TextWidget extends StatelessWidget {
  const TextWidget({super.key}); //  throws error
   final controller = Get.put(TestController());
  
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

it throws an error on the const line :

> Can't define the 'const' constructor because the field 'controller' is initialized with a non-constant value.

so it requires me to delete the const, but since adding const is recommended for better performance, I want to let it there and use my controller.

I could shut down this error by declaring the controller inside the build() method, but I guess it’s not a good idea.

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2

Answers


  1. Chosen as BEST ANSWER
    0

    declaring controllers inside the build() method will cause to extra unnecessary Get.put() that will be called every time widget rebuilds.

    Instead of calling your controller as a variable like this:

    final controller = Get.put(TestController());

    You prevent this error and let your widget const, by using a getter to get the GetxController like this:

    TestController get controller => Get.put(TestController());

    You can use the controller now simply like you will do if you declare it as final, and your widget is still const.

    Consider also using GetView<T> since it makes you achieve the same thing:

    class TextWidget extends GetView<TestController> {
  const TextWidget({super.key});
  @override
  Widget build(BuildContext context) {
    return Text("${controller.index}"); // use controller directly to access controller.
  }
}

    You need just to specify the generic type of your controller with GetView<T>, then you can refer to that controller with the controller getter without defining it manually.


  2. 0

    First of all, create a controller

    class HomeController extends GetxController {}

    Then create an instance of that controller inside the binding

    class HomeBinding extends Bindings {
  @override
  void dependencies() {
    Get.put<HomeController>(HomeController());
  }
}

    Then extends your view with GetView and Assign HomeController to generic type of GetView

    class HomePage extends GetView<HomeController> {
  const HomePage({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Homepage')),
    );
  }
}

    while navigating to that page you can initialize that binding too which will create the instance of that controller

    await Get.to(
  () => const HomePage(),
  binding: HomeBinding(),
);

    you can access variables and functions residing inside HomeController by using controller. and controller. i.e. controller.connectButtonAction(), controller.userName

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