CODEWITHSUNDEEP
flutterdartgenerics
Quentin
Quentin

Reputation: 838

Dart: generic type extending a class with generic types in it

I have a class defined like this:

abstract class QuestionPageBaseState<T extends Question<dynamic, dynamic>> {...

The class Question is defined like this:

abstract class Question<T, U> {...

is it possible to replace the dynamic with a generic type like this?:

abstract class QuestionPageBaseState<T extends Question<U, V>> {...

When I try I get this error: The name 'U' isn't a type so it can't be used as a type argument.

Upvotes: 1

Views: 1516

Answers (1)

Stewie Griffin
Stewie Griffin

Reputation: 5638

You see the error because the compiler doesn't know where the generic type comes from and thinks it's a concrete class (such as int, double, String...); however, it's not.

You can achieve it specifying U and V as type parameters to QuestionPageBaseState which will pass them to Question:

abstract class QuestionPageBaseState<T extends Question<U, V>, U, V> {}

Upvotes: 3

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