I am getting this error "The instance member 'widget' can't be accessed in an initializer." Flutter/Dart

Question

This is my code :

import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';

class viewLossEvent extends StatefulWidget {
  String code,
      
  viewLossEvent(
      {this.code});

  @override
  State<viewLossEvent> createState() => _viewLossEventState();
}

class _viewLossEventState extends State<viewLossEvent> {

  int _selectedIndex = 0;

  void _navigateBottomBar(int index){
    setState(() {
      _selectedIndex = index;
    });
  }

  final List<Widget> _pages = [
    Container(
      child: Text(
          '${widget.code}'
      ),
    ),
  ];

the error that I am getting :

"The instance member 'widget' can't be accessed in an initializer."

I am getting the error right here :

can anyone help solve this and kindly explain why this is happening.

Thank You!

Lilian · Accepted Answer · 2022-08-01T14:45:08.267

3

You cannot initialize a property by using widget.code. You should use initState instead :

List<Widget> _pages = [];

void initState() {
  super.initState();
  _pages = [
    Container(
      child: Text(
          '${widget.code}'
      ),
    ),
  ];
}

edited Aug 01 '22 at 14:45

answered Aug 01 '22 at 14:44

Lilian

56
3

1

This is also a possible approach, but in some cases we'll need to update the `_pages` variable by overriding the `didUpdateWidget` method to keep the variable up-to-date. – Alex Rintt Aug 01 '22 at 14:53
1

Also, welcome to SO @Lilian – Alex Rintt Aug 01 '22 at 15:00

Alex Rintt · Answer 2 · 2022-08-01T14:51:31.483

Always prefer using getters instead fields because Flutter re-uses your state instance across the widget lifecycle and if you keep track the old object references you can face weird and hard to track bugs.

So use instead:

  List<Widget> get _pages => [
    Container(
      child: Text(
          '${widget.code}'
      ),
    ),
  ];

This also best fits the Flutter state management principles.

As you can see this getter will create a new instance of your Container widget every time you access the _pages field, this prevent us from accessing widgets that are not even in the screen anymore, and this approach has no performance issues since it just re-create the widget configuration.

In your case you can also fix the error by using the late modifier (Not recommended due the reasons mentioned above):

  late final List<Widget> _pages = [
    Container(
      child: Text(
          '${widget.code}'
      ),
    ),
  ];

I am getting this error "The instance member 'widget' can't be accessed in an initializer." Flutter/Dart

2 Answers2