About learning Cocoa

February 12, 2006

I first learnt about ObjectiveC and Open/GNUStep when I was basically a Linux user. That was quite a lot of time ago. I was a WindowMaker fan, and that was the way I learnt about GNUStep. However, I did not learn ObjectiveC nor GNUStep programming. In fact there was plenty of “wonderful” languages out there and I felt no need for another one. The few GUI applications I did were made with GTK1 and C (yes, GTK 2 did not exist yet and wx was not really widespread; the first time I installed Audacity on Slackware 8.1 I had to google for them) or Qt with C++.
I was quite skeptical with interpreted languages too: I knew a bit of Lisp (more for academic reasons than for “real programming” — that is to say I would not be able to write a piece of useful software; well, this isn’t changed, anyway) and quite a lot of Perl (still I did not use to do what I considered “serious work”: a few cgi and some system scripting). But I’m going off topic.

One day one of my friends showed me the Powerbook G4 and MacOS X (it was Jaguar, for those who care). After some time I bought my first Mac with MacOS X. Before being a Linux user I was a big fan of MacOS Classic (and the first machine I installed GNU/Linux on was an iMac), so I was really happy with the “new deal” of Apple. Still I planned to “install GNU/Linux as soon as possible”. In fact this never happened (but one of this days when I have time and airport support is stable enough…).
The first thing I did was to learn Objective C. I took a look at Carbon, but I wasn’t amazed. I read Apple’s guides about the language. They were clear and well done. Still to code GUI applications I needed a more detailed book (I’m kind of a perfectionist) since the Tutorial, although well done, is designed for absolute beginners. Anyway the Apple guide for the language ObjectiveC is here.

I still have no idea why I chose to learn it. In fact I was a “cross-platform gui”. I still thought I would use both systems, so having my own applications on both of them was probably quite desirable. Moreover the QT MacOS port was young (it was released a couple of months after I bought the Mac, IIRC).
In the same period I was learning Python too, and almost everything else (system tools, web sites, cross platform gui applications with awful Tk) was made with it. I found some similarities between the two languages (in fact I think they were more similarities between Python and Smalltalk, and only indirectly between Python and ObjectiveC). Still one thing was different. Python is a very high level language, but does not force you in anyway into some kind of framework.

In fact you can perfectly “translate” command line from C using the same POSIX APIs or, for example, “convert” a Qt + C++ program. The language Objective C in fact has the same properties. In fact I wrote a few command line utilities and found that the Foundation kit was a well designed environment that abstracted some POSIX interfaces. I quite liked it. And quite liked ObjectiveC.

The only thing I truly missed were namespaces (or analogue things). I spend a couple of days understanding the memory model and that was everything. I bought two books, “Cocoa in a Nutshell” (today I would not buy this) and “Cocoa Programming” by Anguish Buck and Yacktman. They were both good books. I do not use the Nutshell because Apple documentation is more recent today, not because it’s not well done.
Cocoa Programming” is a “big” book. There are lots of infos. Some of them are advanced topics (for example there are Chapters about optimizations — you know, optimization hinders evolutions, but we want to run our software on something more portable than a mainframe).

The book focuses on how Cocoa was thought with Design Patterns (expecially those from the famous book), even if they change their name (and Anguish/Buck/Yacktman show which Cocoa pattern corresponds to a GOF pattern). I was already acquainted with DP, I read the “Design Patterns: EORSD” some time ago (and recently I bought the book and I’m reading it again). In fact Cocoa developing needs understanding of design patterns, but you can have a less theoretical approach to Cocoa.

I recently read Hillegass’s “Cocoa Programming for MacOS X” and that is what I mean. It’s more like a tutorial, but not as elementar as Apple one. It shows you some “real life” small applications that use key tecnologies. It shows Cocoa structure, main “patterns” (for example how to deal with a NSTableView — and introduces the concept of delegation).
While “Cocoa Programming” shows how much Cocoa can be powerful, Hillegass shows how much Cocoa is easy. There are many things that are not explained in the latter (even if it covers some topics I didn’t find in the other book).

You may need (you probably need) a book like Anguish/Buck/Yacktman’s “Cocoa Programming“, but I strongly advise to start with “Cocoa Programming for MacOS X“. It’s not recent, but it’s well done and complete. You can build a whole lot of applications reading it, and for example explains the Document Based Applications in a very simple yet complete way (for example in “Cocoa Programming” the authors implement classes that act quite like the NSDocument and friends to show you in details how it works, still I was not really able to understand how easy it is programming Doc-based apps with Cocoa; in fact I thought it was hard, since many explanation about how the “true” class works are embedded in the explanation of how to rewrite a subset of it.
Another reason for reading “Cocoa Programming for MacOS X” is its length. Much shorter than the other one, you can read it in less than a week, and dive into programming with more skills. Some useful subjects in “Cocoa Programming” are not at the beginning and you must already know you have to skip chapters and go and read them.
In fact I find the two books complement each other well. I’ve got a third book (well a fourth), but I’m not gonna speak about it this time.

  1. Cocoa Programming” – Anguish/Buck/Yacktman
  2. Cocoa Programming” for MacOS X” – Hillegass
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Apple PyObjC tutorial (Cocoa programming with Python)

February 12, 2006

This is Apple’s tutorial about programming Cocoa with Python. It’s an easy one, but read it if you want to start programming Cocoa with Python. It is quite well done.

Here PyObjC website.


List user defaults in MacOS X

February 5, 2006

The small script below uses PyObjC (it was born as a snippet in ipython to have a quick check to a pair of variables). Of course you can write the very same thing in ObjectiveC.

I strongly encourage to install PyObjC and ipython even if you do work with Cocoa and ObjectiveC, since you can use that to prototype your application and to test snippets of code.


#!/usr/bin/python
# -*- coding: utf-8 -*-

import sys
import Foundation

ud = Foundation.NSUserDefaults.standardUserDefaults()
d = ud.dictionaryRepresentation()

for k in d:
    sys.stdout.write(k)
    sys.stdout.write(":\t")
    try:
        print d[k]
    except UnicodeEncodeError, e:
        print d[k].encode('utf-8')
        
    

To have more information on PyObjC (that is to say Cocoa bindings for Python), go here.

You can find ipythonhere. ipython in an improved interactive shell, with powerful introspection capabilities.
Since MacOS X Python by default comes with no support for readline, I advise to install the missing module for Python 2.3 (search google, I don’t remember right now where to find it) or better install this version of Python 2.4, complete with the patch (on the same page).
Of course you must set your path so that the “first” python is the new one (if you set PYTHON_ROOT and such, you must also fix them).

Remember when you “python setup.py install” a module (that is the typical command line to install a python package), it is installed for the python version called by default (find it out with which pyhon)


Emacs bindings in Cocoa?

January 30, 2006
Key Meaning
ctrl-q Beeps. If pressed twice deletes selection.
ctrl-w Cuts text
ctrl-e Moves to end of line
ctrl-r Beeps??
ctrl-t Swaps near characters
ctrl-y Pastes text
ctrl-u Beeps??
ctrl-i Beeps??
ctrl-o Insert new line after current
ctrl-p Moves cursor to previous line
ctrl-a Moves to beginning of line
ctrl-s Beeps??
ctrl-d Deletes character on the right
ctrl-f Moves forward one character
ctrl-g Beeps??
ctrl-h Deletes character on the left
ctrl-j Beeps??
ctrl-k Cuts line from cursor to the end
ctrl-l Does nothing?
ctrl-z Beeps??
ctrl-x Beeps??
ctrl-c Beeps??
ctrl-v Moves half screen down
ctrl-b Moves backward one character
ctrl-n Moves cursor to next line
ctrl-m Beeps??