How can I define class methods OUTSIDE of the class' brackets to improve readability?

Question

How can I define class methods OUTSIDE of the class' brackets to improve readability? E.g., something similar to this...

class MyClass {
    //Private variables:
    int _foo = 0;
    //Private methods:
    void _incrementFoo();
    //Public methods:
    int getFoo();
}

void _incrementFoo() {
    _foo++;
}

int getFoo() {
    _incrementFoo();
    return _foo--;
}

As you can see, I would like to tell the class about the methods by providing a signature, then I would actually define them outside of the class... Any way to do this in dart?

Answer 1

Well, I don't agree that what you want to do would improve the readability. If you want to split the interface and implementation I think the following are a lot better:

abstract class MyClass {
  //Public methods:
  int getFoo();

  factory MyClass() => _MyClass();
}

class _MyClass implements MyClass {
  //Private variables:
  int _foo = 0;

  //Private methods:
  void _incrementFoo() => _foo++;

  //Public methods implementation:
  int getFoo() => _foo;
}

If you really want to do it you way you need to have a way to tell you method that they are part of you class. You could do something like this:

class MyClass {
  //Private variables:
  int _foo = 0;
  //Private methods:
  void _incrementFoo() => _incrementFooImpl(this);
  //Public methods:
  int getFoo() => getFooImpl(this);
}

void _incrementFooImpl(MyClass myClass) {
  myClass._foo++;
}

int getFooImpl(MyClass myClass) {
  myClass._incrementFoo();
  return myClass._foo--;
}

But I think this is rather ugly and you are ending up adding a lot of global methods in your code which can make it hard to see which class each method are belonging to.