Use Enum.values in with generic class in dart

Question

This question was asked nine years ago for javascript but I couldn't find the answer for the dart. I try to achieve json serialization with enum. There are some solutions with libraries but I want to answer dart logic.

enum GenderType{
  Male,
  Female,
  NonBinary
}

T? getEnum<T>(String key) {
     return (T as Enum).values[_pref?.getInt(key)];
}

I want to write like this. Although I can call GenderType.values, I cannot call them as T.values.

Solution

You can't do this. First of all Enum class doesn't contain values list. The second reason is values in enum is a static field and you can't call static methods or fields on the generic type even you cast them to the specific one.

If you want to create T? getEnum<T>(String key) you can achieve this but in a bad way. So it is just an example:

T? getEnum<T>(String key) {
  if(T == GenderType) {
    //needs some additional checks if _pref is null or getInt(key) returned null
    return GenderType.values[_pref?.getInt(key)] as T;
  }

  //if(T == anotherType) {}
  //and so on

  throw Exception("Unhandled type: $T");
}

But much better to use a separate method for each type.

Comments

[Umut ADALI]

It's not generic type. I don't want to use GenderType in getEnum function. Because there are lots of different enum class like GenderType and this isn't reusable like this code block