Getting type of another generic type from Dart type parameter-CodePudding

I would like to make a generic class which only accepts Lists as a type parameter. But I also want the type parameter of the List. Something like this:

class MyClass<L extends List<T>> {
  T foo() {
    // ....
  }
}

The problem is that that does not work. T is not found. But this does:

class MyClass<L extends List<T>, T> {
  T foo() {
    // ....
  }
}

My only issue with this is that I have to always pass in the extra parameter T which should be inferred from the List type.

var instance = MyClass<List<int>>();

var instance = MyClass<List<int>, int>(); // Extra int kind of redundant

Is there any workaround to this?

CodePudding user response：

The solution is similar to the one provided in this question (the same problem, but in Java): basically, you can't do that in Dart. What you can do is

create a new subclass:

class MyClass2<T> extends MyClass<List<T>, T> { ... }

create a factory method:

class MyClass<L extends List<T>, T> {
  static MyClass<List<T>, T> fromList<T>(List<T> list) {
    return MyClass(...);
  }
}