In Objective-C, nil is defined as a value called __DARWIN_NULL, which essentially evaluates to 0 or false in if-statements. Therefore, writing if (x == nil) is the same as writing if (!x) and writing if (x != nil) is equal to if (x) (since comparing to false creates a negation, and comparing to true keeps … Read more
Use the -isEqualToString: method to compare the value of two strings. Using the C == operator will simply compare the addresses of the objects. if ([category isEqualToString:@”Some String”]) { // Do stuff… }
OK, I will explain your problem, then I will let you judge whether it is a bug in FRC or not. If you think it is a bug, then you really should file a bug report with apple. Your fetch result controller predicate is like this: NSString *predicate = [NSString stringWithFormat: @”clockSet.isOpen == YES”]; which … Read more
It is unsafe to throw exceptions in circumstances where resources are not automatically managed. This is the case of the Cocoa framework (and neighbor frameworks), as they use manual reference counting. If you throw an exception, any release call you skip over by unwinding the stack will result in a leak. This should limit you … Read more
You’ll need to convert the UIImage hosted within your UIImageView into a binary BLOB for storage in SQLite. To do that, you can use the following: NSData *dataForImage = UIImagePNGRepresentation(cachedImage); sqlite3_bind_blob(yourSavingSQLStatement, 2, [dataForImage bytes], [dataForImage length], SQLITE_TRANSIENT); This will generate a PNG representation of your image, store it in an NSData instance, and then bind … Read more
You mean why self = [super init]; rather than [super init]; Two reasons: in initialisation, failure is indicated by returning nil. You need to know if initialisation of the super object failed. the super class might choose to replace the self returned by +alloc with a different object. This is rare but happens most frequently … Read more
Here is what I used to call something I couldn’t change using NSInvocation: SEL theSelector = NSSelectorFromString(@”setOrientation:animated:”); NSInvocation *anInvocation = [NSInvocation invocationWithMethodSignature: [MPMoviePlayerController instanceMethodSignatureForSelector:theSelector]]; [anInvocation setSelector:theSelector]; [anInvocation setTarget:theMovie]; UIInterfaceOrientation val = UIInterfaceOrientationPortrait; BOOL anim = NO; [anInvocation setArgument:&val atIndex:2]; [anInvocation setArgument:&anim atIndex:3]; [anInvocation performSelector:@selector(invoke) withObject:nil afterDelay:1];
Use direct access in partially constructed states, regardless of ARC: – (id)initWithReminder:(Reminder*)reminder_ { self = [super init]; if (self) { reminder = reminder_; // OR reminder = [reminder_ retain]; } return self; } This is because self.whatever will trigger other side effects, such as Key-Value Observing (KVO) notifications, or maybe your class implements (explicitly) or … Read more
It declares a critical section around the code block. In multithreaded code, @synchronized guarantees that only one thread can be executing that code in the block at any given time. If you aren’t aware of what it does, then your application probably isn’t multithreaded, and you probably don’t need to use it (especially if the … Read more
To disable warnings on a per-file basis, using Xcode 3 and llvm-gcc-4.2 you can use: #pragma GCC diagnostic ignored “-Wwarning-flag” Where warning name is some gcc warning flag. This overrides any warning flags on the command line. It doesn’t work with all warnings though. Add -fdiagnostics-show-option to your CFLAGS and you can see which flag … Read more