2

I followed the instructions for installing flutter_reactive_value as described here.

flutter pub add flutter_reactive_value

And I added the import on my main.dart:

import 'package:flutter_reactive_value/flutter_reactive_value.dart';

That's as far as I get.

I am on dart 2.18. I tried it with all versions of this package (1.0.0 - 1.0.3). Also, I downloaded the example (the entire project folder) located here and got the same error listed below. I tried this both as a Flutter web (chrome) and a Flutter Windows app.

Flutter web (Chrome) Error:

Launching lib\main.dart on Chrome in debug mode...
main.dart:1
: Error: The getter 'mounted' isn't defined for the class 'Element'.
reactive_value_notifier.dart:30
- 'Element' is from 'package:flutter/src/widgets/framework.dart' ('../flutter/packages/flutter/lib/src/widgets/framework.dart').
framework.dart:1
Try correcting the name to the name of an existing getter, or defining a getter or field named 'mounted'.
      if (elementRef.target?.mounted ?? false) {
                             ^^^^^^^

Failed to compile application.
Exited (sigterm)

Flutter Windows Error:

Launching lib\main.dart on Windows in debug mode...
../lib/src/reactive_value_notifier.dart(30,30): error G4127D1E8: The getter 'mounted' isn't defined for the class 'Element'. [C:\workspace\flutter_reactive_value\example\build\windows\flutter\flutter_assemble.vcxproj]
C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\MSBuild\Microsoft\VC\v170\Microsoft.CppCommon.targets(247,5): error MSB8066: Custom build for 'C:\workspace\flutter_reactive_value\example\build\windows\CMakeFiles\6f135da36535027a04cd8738f00853c4\flutter_windows.dll.rule;C:\workspace\flutter_reactive_value\example\build\windows\CMakeFiles\335e6badeb606c6fb4bbef90392b261d\flutter_assemble.rule;C:\workspace\flutter_reactive_value\example\windows\flutter\CMakeLists.txt' exited with code 1. [C:\workspace\flutter_reactive_value\example\build\windows\flutter\flutter_assemble.vcxproj]
Exception: Build process failed.
Exited (sigterm)

Any ideas? I am really hoping to use the simple state management that flutter_reactive_value offers. Thanks!

Steve3p0
  • 2,332
  • 5
  • 22
  • 30

1 Answers1

2

You get this error because of this line in flutter_reactive_value package.

The getter mounted, as the error says, isn't defined for the class Element.

Why it is not defined? Because this getter was added to the BuildContext and Element only in flutter 3.7.0(more precisely, in 3.4.0-27.0-pre), and you are using some version below. Here are the release notes.

What can you do?

  1. Upgrade flutter to version 3.7.0 or above
  2. Use flutter_reactive_value package version 1.0.1 or below, because the getter mounted was added to this package in version 1.0.2.
  3. Do not use this package at all. It provides only syntaсtic sugar, and can be replaced by ValueListenableBuilder, which comes out-of-the-box.
Radomir Epur
  • 369
  • 4
  • 4
  • 1
    Thank you! However #2 doesn't work. I tried changing my pubspec.yaml to use version 1.0.1 and 1.0.0, and I get the same error. – Steve3p0 Jul 12 '23 at 10:43
  • 1
    You have to specify the version without the caret symbol(^): flutter_reactive_value package: 1.0.1 If you specify it with caret symbol(^1.0.1) it means that you want to get the latest version of the package between 1.0.1 and 2.0.0(exclusive). And in the end you're getting the 1.0.3(latest compatible at this moment), which is not what you want. See more about caret syntax here: https://dart.dev/tools/pub/dependencies#caret-syntax – Radomir Epur Jul 12 '23 at 11:15