Flutter: Better way to use ObjectKeys?

Question

I am using a StatefulWidget whose constructor contains an Object, like

class X extends StatefulWidget {
  X({this.o});
  Object o;
...
}

As it sometimes happens, this object o changes, but the widget X does not update, so I had to add an ObjectKey in the constructor:

class X extends StatefulWidget {
  X({this.o, this.key});
  Object o;
  ObjectKey key;
...
}

Now every time I call the constructor, I have to call X(o: o, key: ObjectKey(o));. Is there a better way of doing this? It would be nice, if the constructor itself manages that, like

class X extends StatefulWidget {
  X({this.o, this.key = ObjectKey(o)});
  Object o;
  ObjectKey key;
...
}

But as ObjectKey(o) is not a constant expression, it cannot be used as a default parameter. Is there another way?

Answer 1

You can accomplish what you want by using this notation in your constructor:

class X extends StatefulWidget {
  X({this.o}) : key = ObjectKey(o);
  Object o;
  ObjectKey key;
}

This is called the initializer list, which you can find more about here.