Unable to identify the cause of unrecognized selector error

So I'm building this iOS app. Everytime the use taps on a small square that square should change color. I've made sure that all my methods are defined. And I've changed the name of the xIndex value so that I can ENSURE that it isn't the view's .xIndex value that's the source of the crash. But no matter what I seem to do, I still seem to get:

'-[UIView xIndex]: unrecognized selector sent to instance 0x7fe06be6ce70'

Note that the above instance refers to the memory address of specificSquare. Any guesses? Been battling this for hours.

- (void)handleFunViewSquareTap:(UITapGestureRecognizer*)sender
{
    if (sender.state == UIGestureRecognizerStateEnded)
    {
        // handling code
        CGPoint locationOfTap = [sender locationInView: self.view];
        NSInteger xVIndex = floorf(locationOfTap.x / 40.f);
        NSInteger yIndex = floorf(locationOfTap.y / 40.f);

        // find the view that matches these indexes
        for(FunViewSquare *specificSquare in [self.view subviews])
        {
            if((specificSquare.xIndex == xVIndex) && (specificSquare.yIndex == yIndex))
           {
//                //specificSquare.backgroundColor = [ViewController randomColor];
           }
        }
    }
}

- (void)viewDidLoad {
    [super viewDidLoad];

        CGRect frameRect = self.view.frame;
        NSInteger xIndex, yIndex = 0;
        for( CGFloat yPosition = 0.0; yPosition < frameRect.size.height; yPosition+=40.0f )
        {
            // reset xIndex on every iteration
            xIndex = 0;
            for( CGFloat xPosition = 0.0; xPosition < frameRect.size.width; xPosition+=40.0f )
            {
                FunViewSquare *randomSquare = [[FunViewSquare alloc] initWithFrame: CGRectMake(xPosition, yPosition, 40.f, 40.0f)];

                if(randomSquare)
                {
                    randomSquare.backgroundColor = [ViewController randomColor];
                    randomSquare.xIndex = xIndex;
                    randomSquare.yIndex = yIndex;
                    [self.view addSubview: randomSquare];
                }
                xIndex++;
            }
            yIndex++;
        }

        butGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleFunViewSquareTap:)];
        if(butGestureRecognizer)
        {
            [self.view addGestureRecognizer: butGestureRecognizer];
        }

}


+ (UIColor *)randomColor
{
    UIColor *colorToReturn;

    uint32_t randomNumber = random();
    randomNumber = (randomNumber % 10); // a random number between 0 & 10

    switch(randomNumber)
    {
        case 0 :
            colorToReturn = [UIColor blueColor];
            break;
        case 1 :
            colorToReturn = [UIColor grayColor];
            break;
        case 2 :
            colorToReturn = [UIColor greenColor];
            break;
        case 3 :
            colorToReturn = [UIColor purpleColor];
            break;
        case 4 :
            colorToReturn = [UIColor redColor];
            break;
        case 5 :
            colorToReturn = [UIColor brownColor];
            break;
        case 6 :
            colorToReturn = [UIColor cyanColor];
            break;
        case 7 :
            colorToReturn = [UIColor orangeColor];
            break;
        case 8 :
            colorToReturn = [UIColor magentaColor];
            break;
        case 9 :
            colorToReturn = [UIColor whiteColor];
            break;
        default :
            colorToReturn = [UIColor blackColor];

    }
    return(colorToReturn);
}

@end

via Chebli Mohamed