What’s the Best Way to Shuffle an NSMutableArray?

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I solved this by adding a category to NSMutableArray.

Edit: Removed unnecessary method thanks to answer by Ladd.

Edit: Changed (arc4random() % nElements) to arc4random_uniform(nElements) thanks to answer by Gregory Goltsov and comments by miho and blahdiblah

Edit: Loop improvement, thanks to comment by Ron

Edit: Added check that array is not empty, thanks to comment by Mahesh Agrawal

//  NSMutableArray_Shuffling.h

#if TARGET_OS_IPHONE
#import <UIKit/UIKit.h>
#else
#include <Cocoa/Cocoa.h>
#endif

// This category enhances NSMutableArray by providing
// methods to randomly shuffle the elements.
@interface NSMutableArray (Shuffling)
- (void)shuffle;
@end


//  NSMutableArray_Shuffling.m

#import "NSMutableArray_Shuffling.h"

@implementation NSMutableArray (Shuffling)

- (void)shuffle
{
    NSUInteger count = [self count];
    if (count <= 1) return;
    for (NSUInteger i = 0; i < count - 1; ++i) {
        NSInteger remainingCount = count - i;
        NSInteger exchangeIndex = i + arc4random_uniform((u_int32_t )remainingCount);
        [self exchangeObjectAtIndex:i withObjectAtIndex:exchangeIndex];
    }
}

@end

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