Is this a Dart Constructor?

Question

I'm still getting used to Dart and I've searched for an answer to this, but I haven't found one. What does the second line, 'ClassA._();', of the class definition do? The list declaration is only shown to give the class a reason for being.

class ClassA {   
   ClassA._();   
   static final List someList = ["A", "B", "C"]; 
}

If it's a constructor, how would it be invoked? After doing some more sleuthing I see it creates a singleton. But when is the singleton created? Is there a way to get in front of the instantiation and make some mods?

Thanks in advance for any help given.

user_3080848 · Answer

ClassA._();

Is a named constructor with the name _. In dart, identifiers that start with underscore (_) are only visible inside the library it is contained in.

The reason you would define a class this way, is that you want to prevent people from creating instances of this class.

Is this a Dart Constructor?

1 Answers