The parameter 'questions' can't have a value of 'null' because of its type 'List<Map<String, Object>>', but the implicit default value is 'null'

Question

i am new to flutter using VS Code and flutter version - 2.12.0 <3.0.0

My problem is i am passing a list, a function and an int value from one dart class to another using contructor , but getting error in all of them.

1. The parameter 'questions' can't have a value of 'null' because of its type 'List<Map<String, Object>>', but the implicit default value is 'null'.

2. The parameter 'answerQuestion' can't have a value of 'null' because of its type 'Function', but the implicit default value is 'null'.

3. The parameter 'index' can't have a value of 'null' because of its type 'int', but the implicit default value is 'null'.

here is my code -

main.dart

quiz.dart

Thanks for help

Solution

The problem is in the Quiz constructor

Instead of this

const Quiz(
  {@required this.questions,
  @required this.answerQuestion,
  @required this.index});

Declare it like this

const Quiz(
      {required this.questions,
      required this.answerQuestion,
      required this.index});

Comments

[jamesdlin]

You need to replace the old @required annotation with the new required keyword (which was added for null-safety). See dart.dev/null-safety/…

[jamesdlin]

Does this answer your question? what is the difference between required and @required in flutter. What is the difference between them and when do we need to use them?

[jamesdlin]

VS Code seems to be confused, thinking that you're trying to use required from package:meta instead of the required language keyword. That shouldn't happen. Perhaps try restarting VS Code.

[Krishna]

@jamesdlin no sir this didn't helped, did restart many times

[t00n]

add full Quiz code

[jamesdlin]

Post your pubspec.yaml file. Did you somehow change the sdk constraint before changing @required to required? The sdk constraint should be sdk: '>=2.12.0 < 3.0.0'

[Krishna]

@t00n check the link sir

[Krishna]

@jamesdlin it is unchanged ..

[Krishna]

ctxt.io/2/AACgi48TEg @jamesdlin see here

[jamesdlin]

Do you actually have a problem when running your application? Does manually running flutter analyze report the same problems? If no, then again, the problem is that the Dart plug-in for VS Code is confused.

[Krishna]

@jamesdlin ctxt.io/2/AACgN1wyEw

[Krishna]

yes it also shows same error

[jamesdlin]

No, I mean do you have problems running your application and running flutter analyze after replacing @required with required.

[jamesdlin]

Let us continue this discussion in chat.

[Krishna]

@jamesdlin yes sir the above screenshot is after doing @required to required

[Krishna]

sir check the image i have added in the question just now..

[Krishna]

sir check the image i have added in the question just now.