Objective-C Fundamentals

Declared properties
113
Although @synthesize is commonly used in tandem with the @property directive,
its use is entirely optional. The @synthesize directive is intelligent and will generate
getter or setter methods only if it can’t find a suitable method already declared elsewhere
in the @implementation section. This can be helpful if you’d like the compiler
to generate most of your getter and setter methods, but you’d like to override one or
two of them in order to perform special behavior, such as logging or input validation.
An example of this functionality is demonstrated here:
@synthesize rentalPrice;
- (void)setRentalPrice:(float)newRentalPrice {
NSLog(@"You changed the rental per week to %f", newRentalPrice);
rentalPrice = newRentalPrice;
}
In this case, the @synthesize directive generates a getter method for the rentalPrice
property but uses the explicitly specified setRentalPrice: setter.
By default, the @synthesize directive assumes that a property named foo will store
its value in an instance variable also named foo. If for some reason this isn’t desirable,
you can override the name of the instance variable in the @synthesize statement. The
following declaration, for example, synthesizes a rentalPrice property by using an
instance variable called rentalPerWeek:
@synthesize rentalPrice = rentalPerWeek;
Use of the @synthesize directive results in the compiler generating, or synthesizing,
the methods required for a property. Unlike manually written code, the generated
code is well tested, thread safe, and efficient while handling the nuances of memory
management without a second thought from the developer. Using properties not only
reduces the amount of code you need to write but also ensures you avoid common
opportunities to introduce bugs. You can have your cake and eat it too!
5.4.3 Dot syntax
With your current knowledge of Objective-C syntax to obtain the current address of a
rental property, you must send the object an address message, as demonstrated here:
CTRentalProperty *property = ...some rental property...
NSString *address = [property address];
Likewise, you could update the address property by sending the setAddress: message:
CTRentalProperty *property = ...some rental property...
[property setAddress:@"45 Some Lane"];
Objective-C, however, provides an alternative syntax for use with properties. This syntax
is based on the dot (.) operator and may be more comfortable for developers with
a C or Java background:
CTRentalProperty *property = ...some rental property...
NSString *address = property.address;
NSLog(@"Old address is: %@", address);