Mac OS X Leopard - ARCAism

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CHAPTER 26 MAC OS X DEVELOPMENT: OBJECTIVE-C
BMPerson *worldsToughestProgrammer = [[BMPerson alloc] init];
worldsToughestProgrammer.name = @"Mike Lee";
NSLog(@"%@ is the world's toughest programmer.", worldsToughestProgrammer.name);
Mike Lee is the world's toughest programmer.
Notably, properties do not prevent you from using standard syntax:
[worldsToughestProgrammer setName:@"Mike Lee"];
Nor do they prevent you from using KVC syntax:
[worldsToughestProgrammer setValue:@"Mike Lee" forKey:@"name"];
Properties, like scalars, are automatically initialized to nil, so you don’t have to do that in
init, which means, in this case, you don’t need init at all. You also don’t have to explicitly
release your pointers or remember to set them to nil. You can just set the property to nil, which
will do both.
Should you decide to change the way a property behaves, you can just change the property
attributes themselves. The compiler will do the right thing when it comes to the @synthesize
directive. There are three classes of property behavior; see Table 26-4.
Table 26-4. Objective-C 2.0 Property Attributes
Behavior Values Notes
Memory management retain, assign, copy The default is assign.
Mutability readonly, readwrite The default is readwrite.
Thread safety nonatomic atomic is assumed.
The Objective-C way is to make things easy but to allow you to do things the hard way if
necessary. Properties are the same way. If, for example, you have a property whose instance variable
does not have the same name, you can connect the two explicitly. For example, if, in
BMPerson, you called the property age but the ivar years, you could note this in your @synthesize
directive:
@synthesize name, age = years;
If you wanted to override the setter of the age property to provide validation, all you have
to do is implement it:
- (void)setAge:(NSUInteger)anAge;
{
if (anAge > 0 && anAge < 100)
age = anAge;
}
Even though you’ve asked the compiler to synthesize this property, it will see that you’ve
implemented it yourself and do the right thing.
In the converse of assigning an ivar, you can also, if necessary, explicitly assign a setter or
getter in the property declaration:
@property (assign, getter=ageInYears) NSUInteger age;