[Pyobjc-dev] Documentation submission...

[Jiva D. <ji...@de...>]

I would like to respectfully submit the following  
clarification/documentation for the docs page on  
pyobjc.sourceforge.net.  (Credit to bbum for the basics, all I am  
adding is some example code to make it clear.)

---------

  Instantiating Python Classes from Obj-C

First, follow these  
instructions:http://pyobjc.sourceforge.net/doc/ 
extending_objc_with_python.php to add python to your PyObjC app.

Ok, that's the hard part. From here, everything is easy.  Once you have  
imported your Python class, you can do this:

  @class MyPythonClass

  @implementation MyObjCClassCallingMyPythonClass

  -(void)aMethod
  {
     id myPythonObj = [[MyPythonClass alloc] init];
     [myPythonObj someMethodInPython];
  }

  @end

Assuming you have a "MyPythonClass" defined in a python module in your  
resources directory.

What this means, is basically PyObjC magically does it for you. Nothing  
else is needed.

Now this will all work, and as long as you don't mind warnings when  
compiling... this is great. But, being obsessive about such things, we  
probably want to get rid of the compile warnings we're getting.

To solve this problem, use an abstract superclass implemented in  
Objective-C (a class that simply declares all the methods where the  
implementation is stubbed out) and a concrete subclass implemented in  
Python. To the abstract superclass-- the objc class-- add a factory  
method that instantiates and returns the concrete subclass.

So in other words to make Obj-C not complain about your undefined  
methods, you need to create an abstract superclass with a constructor  
that looks something like this:

  -(id)init
  {
      self = [[MyPythonClass alloc] init];

      return self;
  }

Or something along those lines.

With this code, you should be able to instantiate your abstract  
superclass and get everything you need with no warnings!

Viola!
--
Jiva DeVoe
jiva at devoesquared.com
http://www.devoesquared.com