Re: [Pyobjc-dev] Inheritance questions....

[Bob I. <bo...@re...>]

On Apr 14, 2004, at 4:59 PM, Jiva DeVoe wrote:

> How do I call functions in a class which inherits from an objc class 
> *before* i have finished initializing self?  My goal here is to call 
> some subfunctions in my constructor before calling the inherited 
> constructor.  But self is not yet initialized, so it doesn't work...

You don't.  You want class methods.

> So, say I have the following code in a python file:
>
> from Foundation import *
> from AppKit import *
from objc import selector

> class BaseView(NSView):
>     def __new__(cls, *args, **kwargs):
>         return cls.alloc().init()

Is this really a good idea?

>     def initWithFrame_(self, frame):
>         super(BaseView, self).initWithFrame_(frame)
>         return self

self is allowed to change after an init call!

     def initWithFrame_(self, frame):
         self = super(BaseView, self).initWithFrame_(frame)
         return self

>     def initWithPrintInfo_(self, info):
>         self.info = info
>
>         self.frame = self.getFrameFromPaperSize(info.papersize())
>
>         self.initWithFrame_(frame)
>
>         return self

Note that you did misspell paperSize ...

     def initWithPrintInfo_(self, info):
         frame = self.__class__.getFrameFromPaperSize_(info.paperSize())
         self = self.initWithFrame_(frame)
         return self

>     def getFrameFromPaperSize(self, size):
>         return ((0, 0), (10, 10))

     def getFrameFromPaperSize_(klass, size):
         return ((0, 0), (10, 10))
     # this should technically have a signature that returns NSRect and 
takes NSSize.
     # I'll leave that as an exercise to the reader
     getFrameFromPaperSize_ = selector(getFrameFromPaperSize_, 
isClassMethod=True)

> class Inherit1(BaseView):
>     def getFrameFromPaperSize(self, size):
>         return ((0, 0), (20, 20))

     def getFrameFromPaperSize_(klass, size):
         return ((0, 0), (20, 20))
     # the selector wrapper is not necessary here, it'll get picked up 
because we're subclassing