Question

I have created the following Singleton in my iPhone app:

#import "AppManager.h"

static AppManager *sharedAppManager = nil;

@implementation AppManager

@synthesize currentType, listOfTypes;

#pragma mark Singleton Methods
+ (id)sharedManager {
    @synchronized(self) {
        if (sharedAppManager == nil)
            sharedAppManager = [[self alloc] init];
    }
    return sharedAppManager;
 }
- (id)init {
    if (self = [super init]) {
        currentType = @"";
        listOfTypes = [NSArray arrayWithObjects:@"T1", @"T2", @"T3", nil];
    }
    return self;
}
- (void)dealloc {
    // Should never be called, but just here for clarity really.
    [currentType release];
    [listOfTypes release];
    [super dealloc];
}

@end

When I use it:

// TEST
AppManager *appManager = [AppManager sharedManager];
NSArray *array = appManager.listOfTypes;
NSLog(@"TYPES:%@", array);

I have a strange thing…

TYPES:<UIButtonContent: 0x7b8db10 Title = (null), Image = <UIImage: 0x7bad7f0>, Background = (null), TitleColor = UIDeviceWhiteColorSpace 1 1, ShadowColor = UIDeviceWhiteColorSpace 0 0.5>

It’s working fine with currentType (NSString property) but it does not with listOfTypes (NSArray)

Answer 1

You are not retaining the array listOfTypes, so the array probably got released and is pointing to some garbage value. Use the following to retain the array (if it is a retained/copied property).

self.listOfTypes = [NSArray arrayWithObjects:@"T1", @"T2", @"T3", nil];

You can also simply send the retain message to the array.

listOfTypes = [[NSArray arrayWithObjects:@"T1", @"T2", @"T3", nil] retain];

or allocate the array.

listOfTypes = [[NSArray alloc] initWithObjects:@"T1", @"T2", @"T3", nil];