Objective-C for AS3.0 Developers: How to create a new object

In AS3.0 you create a new Object, or instance of a Class, and store it in a reference (or variable) like so:

private var myRef:MyClassName = new MyClassName();
private var myRef:MyClassName = new MyClassNameSubclass();

In Objective-C 2.0, there’re several ways to do this.

Here’s 1 way:

MyClassName *myRef = [[MyClassName alloc] init];

Here’s another:

MyClassName *myRef; //create the reference/variable
myRef = [MyClassName alloc]; //allocate memory of size MyClassName
myRef = [myRef init]; //initiate the MyClassName instance called myRef

And another:

MyClassName *myRef = [MyClassName new];

Why do we have to bother allocating memory manually? AS3.0 developers should be familiar with the concept of Garbage Collection. Objective-C does support GC but not everywhere. For example, the iPhone doesn’t allow it, apparently because of concerns over battery life.

In case you’re wondering, alloc and init are methods inherited from NSObject. Most Objective-C classes in the Foundations Framework inherit from NSObject.

Objective-C 2.0 also allows for dot (.) syntax that Flash/Flex/Actionscript developers are used to.

However, it seems like object instantiation doesn’t fully work with dot syntax. I’m no expert but when I try to write “MyClassName.alloc()” or “MyClassName.alloc” I get errors.
This worked, however:

NSAutoreleasePool * pool = [NSAutoreleasePool alloc]; 
pool = pool.init; 

MyClassName *myRef =  [MyClassName alloc];
myRef = myRef.init;

I’m guessing this means that dot syntax works with Instance methods but not with Class methods.

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