nsnumber

After successfully acquiring a picture from the iPhone camera on iOS 4.1, you can use the key @"UIImagePickerControllerMediaMetadata" to return information about the picture. One of the keys in that dictionary is @"Orientation" From my experimentation, Portrait and Upside down are 6 and 8 respectively, and the landscapes are 1 and 3. Look at this code: - (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info { NSDictionary *metaData = [info objectForKey:@"UIImagePickerControllerMediaMetadata"]; id orientation = [metaData objectForKey:@

Let's say I have an NSArray of NSNumbers like this: 1, 2, 3 Then the set of all possible permutations would look something like this: 1, 2, 3 1, 3, 2 2, 1, 3 2, 3, 1 3, 1, 2 3, 2, 1 What's a good way to do this in objective-c? I have used the code from Wevah's answer above and discovered some problems with it so here my changes to get it to work properly: NSArray+Permutation.h @interface NSArray(Permutation) - (NSArray *)allPermutations; @end NSArray+Permutation.m #import "NSArray+Permutation.h" #define MAX_PERMUTATION_COUNT 20000 NSInteger *pc_next_permutation(NSInteger *perm, const NSInteger

Given the following code: int firstInt, secondInt; firstInt = 5; secondInt = 5; NSNumber *firstNumber = [NSNumber numberWithInt:firstInt]; NSNumber *secondNumber = [NSNumber numberWithInt:secondInt]; Why on Earth do those two NSNumber instances are pointing to the same address? This drives me crazy! Of course, if you change secondInt to, say '4', all works as expected. Thanks, Jérémy This is likely either a compiler optimisation or an implementation detail: as NSNumber is immutable there's no need for them be separate instances. EDIT: probably an implementation optimisation thinking about it.

What's the difference between NSNumber and NSInteger? Are there more primitives like these that I should know about? Is there one for floats? Tyler The existing answers are useful; adding to them: Yes, NSUInteger gives twice the range among positive integers as NSInteger , but I think another critical reason to choose between the two is simply to distinguish among cases where negative values simply do not make sense . Example: the return value of NSArray 's count method is an NSUInteger , which makes sense since we cannot have an array with a negative number of elements. When the coder knows