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POHow can I shuffle an NSArray?
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  1. POHow can I shuffle an NSArray?
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    copied!<p>All examples I find on shuffling arrays are for NSMutableArrays. Copying an NSArray to an NSMutable array, shuffling, then copying back always crashes the application. Is it even possible to shuffle an NSArray?</p> <p>Anything in objective-c similar to Collections.shuffle() (Java)?</p> <h2>Edit</h2> <pre><code>static NSUInteger random_below(NSUInteger n) { NSUInteger m = 1; do { m &lt;&lt;= 1; } while(m &lt; n); NSUInteger ret; do { ret = random() % m; } while(ret &gt;= n); return ret; } - (NSArray *)loadAllData{ XYZAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate]; NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext; NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Quote" inManagedObjectContext:managedObjectContext]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"id" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; [request setEntity: entity]; NSError *myError; NSArray *theResults = [managedObjectContext executeFetchRequest:request error:&amp;myError]; if (theResults == nil) { NSLog(@"Testing: No results found"); }else { NSLog(@"Testing: Results found."); } [request release]; [sortDescriptors release]; for(NSUInteger i = [theResults count]; i &gt; 1; i--) { NSUInteger j = random_below(i); [theResults exchangeObjectAtIndex:i-1 withObjectAtIndex:j]; } return theResults; } warning: 'NSArray' may not respond to '-exchangeObjectAtIndex:withObjectAtIndex:' which crashed the application. error: *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[_PFArray exchangeObjectAtIndex:withObjectAtIndex:]: unrecognized selector sent to instance 0x3d35a40 </code></pre>
 

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