Mac OS X Leopard - ARCAism

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CHAPTER 26 MAC OS X DEVELOPMENT: OBJECTIVE-C
As with init, you’re overriding your superclass’s implementation. Sending a dealloc message
to super will give everyone in the inheritance tree a chance to take care of their final business
as well. With init, we typically call super first. In dealloc, we call super last.
With the inherited hassle of memory management out of the way, you can finally get back
to all those instance methods you declared.
Instance Methods
The whole point of object-oriented programming is to transfer responsibility to your objects.
Whereas a functional programmer might say, “I am going to do something with this,” an objectoriented
programmer would say, “I am going to ask this to do something.” The tasks we can ask
our objects to do are their instance methods.
The most common instance methods are for directly accessing and mutating an object’s
instance variables. In technical terms, we call these methods accessors and mutators, but Apple
prefers the more colloquial setters and getters. Whatever you call them, these methods follow a
standard pattern.
- (NSString *)name;
- (void)setName:(NSString *)aName;
In Objective-C, a getter has the same name and return type as the ivar it’s accessing and
takes no arguments. The setter adds the prefix set to the name, takes one argument of the ivar’s
type, and returns nothing. For the special case of Boolean ivars, the getter may use the prefix is.
For example, calling isHidden would access the ivar hidden.
NOTE Some languages will precede the ivar name with the word get, but in Objective-C, you
use that pattern for something else.
At its simplest, a getter just returns the value of the ivar:
- (NSString *)name;
{
return name;
}
Because of memory management, setters are a bit more complicated:
- (void)setName:(NSString *)aName;
{
if (name == aName)
return;
}
[name release];
name = [aName retain];
The first thing you’ll notice is a setter’s argument cannot have the same name as its ivar.
Looking at the first line explains why that is:
if (name == aName)
If you had given the argument the same name, you’d end up with this:
if (name == name)
Wouldn’t that be confusing?