First Glance at Objective-C and the iPhone SDK (by a Java and C Developer)

http://webbtech.posterous.com/a-java-developers-first-glance-at-objective-c

by webb • 15 years ago

27 22 15 years ago

webbtech.posterous.com

spearo77• 15 years ago

While that's a decent summary of his current perspective, I'd wager that the biggest adjustment won't be memory management. Although that is a trap for new players, a bigger adjustment will be to think and code in the "Cocoa-way".

In my experience, Cocoa Touch has all the benefits of it's very mature Mac OS foundation, and to develop effectively, and minimise friction, you need adhere to the Cocoa way.

sigzero• 15 years ago

I thought ObjC had garbage collection now?

BigZaphod• 15 years ago

Only on the Mac. I guess Apple feels the memory and/or performance cost is still too high for mobile.

webb2• 15 years ago

I don't know the history here, but based on the autopool directives it looks like they toyed with the idea.

jinushaun• 15 years ago

I totally agree. All the quirks and idiosyncrasies of ObjC go away after a week of coding in it. What's more difficult to adopt is Apple's Cocoa framework. Coming from a background of most UI frameworks, Cocoa is just simply different from anything else out there. You're gonna find yourself going to developer.apple.com and stackoverflow.com for even the most basic tasks. It requires a different way of thinking about problems because the solutions are so different. Developers who have only dabbled in MVC will find themselves forced to adopt MVC and all its overhead for applications large and small.

wallflower• 15 years ago

A lot of my problems with learning Cocoa was when I fought the framework. Don't fight the framework, save yourself time.

jimbokun• 15 years ago

"Message (function call) syntax seemed funky."

"When I first realized the language offered weak typing -- with the (id) variable -- it seemed to go against everything that C stood for in my mind."

These are good observations, and reflect deliberate choices in the design of Objective C.

The funky message syntax makes clear that a sending a message is not equivalent to calling a function. Conflating the two will eventually lead to pain and confusion.

Declaring a variable as "id" does indeed launch you out of C's type system, into a realm where any object can potentially respond to any message, regardless of its type. This leads to a lot of interesting possibilities and patterns that Cocoa (and iOS) leverage heavily.

othermaciej2• 15 years ago

Sending a message is indeed equivalent to calling a function, specifically the function objc_msgSend (or one of its variants, depending on return type).

It's also very much like calling a virtual function in C++, only slower.

js22• 15 years ago

In the normal case it's still very fast http://www.friday.com/bbum/2009/12/18/objc_msgsend-tour-part...

shadowmatter• 15 years ago

I started about a month ago... As someone with a background in Java/C++/Python, here are some more that have caught my attention:

- The ability to assign types as ClassName<Protocol>, instead of the protocol specifying the type completely. Neat, I guess...

- Because it's message passing, you get duck typing for free, albeit with compiler warnings (you send a message, and wouldn't you know it, the selector exists!). Not that I recommend this approach over protocols.

- The awesomeness of @selector, especially if you're coming from Java and used to writing anonymous classes everywhere simply for the sake of making functions first-class entities.

- The lack of public/protected/private visibility modifiers and how variables are suddenly part of the public API when you define them in properties. Say you have a variable you want to keep private, but you need to frequently update its value. You go ahead and define @property (nonatomic, retain) for it so within the class so that you can simply do self.varName = newVarValue to update it. But now all your clients/outside clients will see; you need to write the release-and-retain setter yourself in the .m file to prevent this.

- The minimalism of Xcode. Hey, it's faster than Eclipse, thank $DEITY for that. But when I want to alphabetize the filenames in the left sidebar, I have to go to Edit -> Sort -> By Name for _every_ file group?

betamike• 15 years ago

You can define a category within your implementation file (.m) and redeclare the property like this:

@interface MyClass (PrivateMethods)

@property(readwrite, retain) NSObject *myProperty;

@end

@implementation MyClass ...

Now only your implementation knows about the generated setter methods, and you don't have to implement them yourself.

rbritton• 15 years ago

You can use @public, @private, or @protected on the instance variables. Unfortunately these do not extend to the properties themselves and you have to use a different approach as in the sibling comment:

  @interface SomeClass (SomePrivateCategory)
     @property (nonatomic, assign) NSUInteger count;
     ...
  @end

chc3• 15 years ago

Actually, Objective-C has class extensions for just this purpose. No need for a private category.

ianl• 15 years ago

One of the biggest pitfall for beginners is the fact you can send messages to nil objects.

Secondly, while this is minor, I find it annoying that when declaring array's I have to include nil at the end.

ary• 15 years ago

Exactly when and where did Apple suggest not to use NSAutoReleasePool?

webb2• 15 years ago

I know this is a broad statement on my part. Apples says the following in the hello world tutorial, "In general, however, you should try to avoid using autorelease wherever possible since it means memory may be reclaimed later than it would be if you used release."

First Glance at Objective-C and the iPhone SDK (by a Java and C Developer)

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