Objective-C Fundamentals

120 CHAPTER 5 Creating classes
One thing to note is that, although declared properties can automatically provide
getter and setter implementations, they won’t generate code in dealloc to free their
associated memory. If your class contains properties using retain or copy semantics,
you must manually place code in your class’s dealloc method to clean up their memory
usage. In listing 5.8 this is demonstrated by the address property. When destroying
a rental property object, you want the copy of the address string you made in the
property’s setter to be cleaned up.
Finally, most dealloc method implementations end with a call to [super dealloc].
This gives the superclass a chance to free any resources it has allocated. Notice
that the order here is important. Unlike with an init implementation, where it’s
important to give the superclass a chance to initialize before you initialize your own
content, with a dealloc method, you must tidy up your own resources, and then give
the superclass a chance to tidy up.
5.6 Using the class in the Rental Manager application
Now that you’ve created a class called CTRentalProperty and gone through various
iterations to improve its source code, let’s update the Rental Manager application.
The first step is to open RootViewController.h and remove the existing definitions
for the PropertyType enumeration and RentalProperty structure. Replace them with
the CTRentalProperty class. At the same time, you can add an NSArray-based instance
variable to store the list of rental properties. With these changes made, you should
end up with RootViewController.h looking similar to the following listing.
Listing 5.9
RootViewController.h storing rental properties in an object-oriented manner
@interface RootViewController : UITableViewController {
NSDictionary *cityMappings;
NSArray *properties;
}
@end
Using an NSArray to store the rental properties enables you to eventually add and
remove properties while your application runs. This is something you can’t easily do
with the C-style array used previously.
In comparison, RootViewController.m requires a number of larger source code
changes, so replace its existing contents with the following listing.
Listing 5.10
RootViewController.m updated to use the CTRentalProperty class
#import "RootViewController.h"
#import "CTRentalProperty.h"
@implementation RootViewController
- (void)viewDidLoad {
[super viewDidLoad];
b
Import the CTRentalProperty
definition
NSString *path = [[NSBundle mainBundle]
pathForResource:@"CityMappings"