Question

I’m an Objective-C newbie and I’m reading “iPhone programming” by Alasdair Allan. While reading, I found this code:

@interface RootController : UIViewController <UITableViewDataSource, UITableViewDelegate> {
    UITableView *tableView;
    NSMutableArray *cities;
}
// warning: remember this tableView
@property (nonatomic, retain) IBOutlet UITableView *tableView;

The relative implementation starts this way:

@implementation RootController
@synthesize tableView;

Now: I learnt that @synthesize is a sort of shortcut to avoid boring getters and setters.

But I’ve some question:

1. in the code of the implementation tableView is never explicitly called but the dealloc releases it;
2. if it never gets called explicitly why the @synthesize?

Is it mandatory for IBOutlets to be synthesized?

Answer 1

From Memory Management of Nib Objects,

When a nib file is loaded and outlets established, the nib-loading mechanism always uses accessor methods if they are present (on both Mac OS X and iOS). Therefore, whichever platform you develop for, you should typically declare outlets using the Objective-C declared properties feature.

For iOS, you should use:

@property (nonatomic, retain) IBOutlet UIUserInterfaceElementClass *anOutlet;

You should then either synthesize the corresponding accessor methods, or implement them according to the declaration, and (in iOS) release the corresponding variable in dealloc.