Category on an NSArray to return n random elements.

gistfile1.m

@interface NSArray (MPV)
- (NSArray*) mpv_randomElements:(NSUInteger)maxElements;
@end

@implementation NSArray (MPV)

- (NSArray*) mpv_randomElements:(NSUInteger)maxElements {
    
    NSUInteger numElementsToPick = MIN(self.count, maxElements);

    NSMutableArray *outArray = [NSMutableArray arrayWithCapacity:numElementsToPick];
    NSMutableArray *srcArray = [self mutableCopy];
    
    while (outArray.count < numElementsToPick) {
        NSUInteger randomIndex = arc4random() % srcArray.count;
        id randomObject = srcArray[randomIndex];
        [outArray addObject:randomObject];
        srcArray[randomIndex] = [srcArray lastObject];
        [srcArray removeLastObject];
    }
    
    return outArray;
}

@end