Monday, August 28, 2006

Thoughts on Objective-C 2.0

One of the most exciting changes coming in Mac OS X Leopard, is the new xCode 3.0 with a major update of the Objective-C language. While I think Objective-C is a great programming language and Cocoa is a great framework, it is getting a little bit long in the tooth in a few places.

This has attracted considerable bashing from different people. Nitesh Dhanjani of O'Reilly for instance started a big debate about whether Apple should offer more choices to developers.

The basic argument is that Microsoft is way ahead of the curve with C# and the .NET framework. .NET allows developers to choose any language in theory, thus giving them more choice. This is not something apple offers at the moment.

However with Objective-C 2.0 it seems like Apple has narrowed the gap to more modern languages like C# and Java. It is not official yet but it seems like Objective-C will offer:

  • Optional garbage collection. This was actually an option in Tiger, but toggling it didn't do anything.
  • for each statement. Which makes iterating through objects in containers easier. This is similar to the C# for each.
  • Properties. You don't need to explicitly use setter and getter methods. If you access or set a variable, access methods will be used if they are defined.
  • Method attributes. Not so sure about this but apparently it is similar to what is found in C#.

Here are some examples of the new syntax. The for each syntax:

NSArray *arr = randomListOfStrings();
for (NSString *s in arr) {
  NSLog("%@\n", s);

And here is an example of properties:

@interface MyClass : NSObject {
  int   foo;
  float baz;

@property int foo;
@property(getter=_getBaz,setter=_setBaz) float baz;


@implementation MyClass

@synthesize foo;

- (int)_getBaz { return baz; }
- (void)_setBaz: (float)newBaz { baz = abs(newBaz); }


int main(void) {
  MyClass *m = [MyClass new];
  m.baz = -5.0;
  printf("%f\n", m.baz); /* -> 5.0000 */

I think this means that Mac developers don't have to consider themselves second class citizens. Although I think it never was that bad. A lot of the advantages of .NET and C# are highly theoretical.

Even though you can make any language that language is still limited in functionality to that of the IL code and the .NET framework. The Cocoa framework exploits a lot of the particular strengths of the Objective-C language. It would be difficult to make a framework similar to Cocoa within the .NET world.

So far it seems like most .NET developers are using C#. The other major .NET languages offer little extra functionality or benefits.

Even if Apple does not have an IL type language on which to build other languages they are not really that trapped in language offerings. Because of the highly dynamic nature of Objective-C which is based on message passing instead of method invocation. Other dynamic languages can easily be made to interface with Objective-C classes. Some examples are Ruby Cocoa and PyObjC, which is a Python bridge to Cocoa. One only needs to create a bridge or in other words code that translates the message passing in Objective-C to that of the other language. E.g. in Java there needs to be defined a type for each Objective-C class to maintain the bridge. Unknown Objective-C classes can not be used. For more in-depth look at the problems with bridging Objective-C and Java look at cocoadev.


Another important point is that I think Objective-C is simply a much more versatile language than C#. Although high performance can be squeezed out of C# it is not nearly as easy. "Easy" is a keyword here, because no language can really do anything another language can't. All popular programming languages today are Turing complete. The difference is then about with what flexibility, ease and performance one can do a certain task.

In a lot of language you can create modules written in C for critical sections and call them from the "mother" language. You can do this in Java through Java native calls. In Ruby you can add your own classes written in C. In C# you can mix managed and unmanaged code. E.g. you can have certain sections written in plain C++.

However the ease which one does this differs. Objective-C is a superset of C and interacts with it easily. Writing performance intensive parts of the program is thus easy and straight forward. One simply tries to use as much plain C as possible and as little object oriented features.

The same can not be said about .NET. I have learned the hard way that mixing managed and unmanaged code is no trivial task. It looks easy in theory and doesn't seem that hard when one does it with small example code. But as soon as you have to deal with a large real world application, problems start piling up.

This means that for performance critical tasks it will be much easier to fine tune a Objective-C application than a .NET application.

Missing features from Objective-C

So if the rumors are right, what will be missing from Objective-C to make it competitive with C# and other modern languages? I could actually only thing of one thing and that is support for namespaces. At the moment this is solved by prefixing class and function names with two letters, to distinguish them from classes and functions with the same name.

Some might argue templates or generics is missing but that is only something that is needed on a static language like C++, Java and C#. In Objective-C data types (except primitives) can be easily inserted and accessed from a container class. No up-casting is needed.


Mac development is going to be better than ever. The only thing that I miss now is a better IDE. I think the debugger in xCode has a lot of problems. It should be improved and so should code completion. Code navigation and re-factoring support could also be improved. At the moment I use TextMate a lot for my coding because it is a lot faster to jump around in code. Apple+T brings up a window that does name completion of files so I can jump to a new file with some quick typing. it also does tabs.

Perhaps Apple should simply improve the integration of the code editor with third party tools. For instance allows some hooks so that after a failed build one can jump to errors in an external code editor.

Also they should do something to reduce the amount of windows that are open at any given time. I do like multiple windows because it allows you to organize your work more when you have a lot of screen real-estate. But at the moment it just seem to become too many windows to keep track of: debug window, code window, run window, console window, project window etc.

If not reducing the number of windows at least provide a better way of managing them (although I guess Spaces might solve a lot of the problem).

My last wish is that Cocoa method names was a bit shorter. Do we really need:

[array insertObject:obj atIndex:2];

Isn't it just as readable to simply write:

[array insert:obj at:2];

Actually I find it almost hard to read Objective-C code at times because the Cocoa method names are so long that you can't actually glaze at them to see that they say. E.g. "thisIsAVeryLongMethodNameIndeed" takes some time to read. Of course this is all wishful thinking because it is too late to change the names not. But one can always dream.

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