[skybrian]

I haven't seen a GUI written in Go yet, but the basic idea is that you don't customize via inheritance; you do it in a different way. For example, in many UI libraries, you can create a function and ask a widget to call you when you receive an event; the widget will have methods like:

  addClickHandler(myFunction)

Any customization you could do with inheritance could be done with a callback function instead, provided that the object has the hook you want.

In Go, there is also an "interface" which is basically a set of methods.

[LinaLauneBaer]

That is more or less how UIs using Cocoa/Cocoa Touch are working from a developer standpoint of view. Most standard views/controls have a delegate property which is informed about certain things happening or asked when an important decision has to be made. This works extremely well and by implementing a delegate you get around the problems related to subclassing UI controls/views. Now that Objective-C/C has blocks Apple began to replace (or add) block based "callbacks" which makes life easier in most cases.