Question

I have a string (currently defined in my .h file) that I’d like to fill and reuse in my .m file.

Here’s the setup:

1. User clicks btnA in my interface
2. btnA runs a method (buttonAClicked) that sets the NSString’s value to “foo”
3. USer clicks btnB in my interface
4. btnB runs a method (buttonBClicked) that returns the value of the NSString (eg: “foo”)
5. User clicks btnA again and the method updates the NSString “a new value”…
6. Profit!

Here’s some code:

/* Modal_TestAppDelegate.h */
// in the @interface block //
@public
NSString *countOfMatches;
// in the main area of the .h //
@property (nonatomic, readwrite, reatain) NSString *countOfMatches;
/* Modal_TestAppDelegate.m */
@synthesize countOfMatches;
-(void)applicationDidFinishLaunching:(UIApplication *)application{
... other code ...
self.countOfMatches = [[NSString alloc] initWithFormat:@"0"];
}
-(void)updateButtonClicked:(id)sender{
countOfMatches = @"1";
NSLog(@"countOfMatches is now: %@",countOfMatches);
}
-(void)readButtonClicked:(id)sender{
NSLog(@"I wonder what countOfMatches is set to now? %@",countOfMatches); // CRASH!
}

the “readButtonCicked area is where I’m crashing – it looks like I can’t read the countOfMatches string anymore.

Any ideas on how I can simply reuse a “variable” throughout a single class (if I’m calling the .m implementation a “class” correctly – this is my first attempt and I’m kinda ripping pages out of the several Xcode and iPhone SDK books I have).

Thanks!

Answer 1

You should set your NSString property to copy, not retain. (More here)

@property (nonatomic, readwrite, copy) NSString *countOfMatches;

You’re also leaking memory on this line

self.countOfMatches = [[NSString alloc] initWithFormat:@"0"];

It could be

self.countOfMatches = [[[NSString alloc] initWithFormat:@"0"] autorelease];

or even better:

self.countOfMatches = [NSString stringWithFormat:@"0"];

or even best (and really, what it should be):

self.countOfMatches = @"0";

There’s no sense using any of the “format” methods of NSString — you’re just setting it to a static string.