I can not remember many examples of extended objects for Nim. For OO languages
like Ruby we can extend everything with arbitrary custom fields. For Nim
standard types I have never seen something like
type
MyStr = ref object of string
age: int
var m: MyStr = newString(); m.age = 7
Well, composition over inheritance?
But for the high level GTK proxy objects I need the ability to extend objects
of course, otherwise the high level wrapper makes not much sense at all.
Currently I have all the GUI objects working fine, with procs like newButton()
the Nim button proxy object linked with the real GUI element is created. But
now users may want to add new fields to the elements, so I need a proc like
initButton()? I know we have some init procs in standard lib like initTable(),
but I think that name is more about value and reference objects.
I just tried code like this:
type
O = ref object of RootObj
i: int
O1 = ref object of O
j: int
proc newO(): O =
new(result)
result.i = 7
proc initO[T](o: var T) =
assert(o is O)
new(o)
o.i = 7
var o = newO()
echo o.i
var o1: O1
initO(o1)
o1.j = 9
echo o1.i
echo o1.j
#var o1x = initO[O1] # does not work
Well, I think that is what may be desired, so for each GUI widget XXX I can
provide beside a newXXX() proc a initXXX() proc which accepts extended objects.
Is there a way to reduce
var o1: O1
initO(o1)
into one single statement? The commented out from above (#var o1x = initO[O1])
does not work of course.
