gistfile1.m

- (void)createTriangles {
    UIView *triangleWrapper = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.collectionView.frame.size.width, self.collectionView.frame.size.height)];
    [self.collectionView addSubview:triangleWrapper];
    
    CGFloat radius = MIN(self.collectionView.frame.size.width, self.collectionView.frame.size.height) / 2.5;
    CGPoint center = triangleWrapper.center;
    
    for (NSInteger i = 0; i < [self.collectionView numberOfItemsInSection:0]; i++) {
        CGPoint point1 = CGPointMake(center.x + radius * sinf(2 * (i - 0.5) * M_PI / [self.collectionView numberOfItemsInSection:0]),
                                     center.y + radius * -cosf(2 * (i - 0.5) * M_PI / [self.collectionView numberOfItemsInSection:0]));
        
        CGPoint point2 = CGPointMake(center.x + radius * sinf(2 * (i + 0.5) * M_PI / [self.collectionView numberOfItemsInSection:0]),
                                     center.y + radius * -cosf(2 * (i + 0.5) * M_PI / [self.collectionView numberOfItemsInSection:0]));
        
        UIBezierPath* trianglePath = [UIBezierPath bezierPath];
        [trianglePath moveToPoint:CGPointMake(center.x, center.y)];
        [trianglePath addLineToPoint:CGPointMake(point1.x, point1.y)];
        [trianglePath addLineToPoint:CGPointMake(point2.x, point2.y)];
        [trianglePath closePath];
        
        CAShapeLayer *triangleMaskLayer = [CAShapeLayer layer];
        [triangleMaskLayer setPath:trianglePath.CGPath];
        
        UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0,0, triangleWrapper.frame.size.width, triangleWrapper.frame.size.height)];
        
        CGFloat hue = ( arc4random() % 256 / 256.0 );  //  0.0 to 1.0
        CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5;  //  0.5 to 1.0, away from white
        CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5;  //  0.5 to 1.0, away from black
        UIColor *color = [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:1];
        
        view.backgroundColor = color;
        view.layer.mask = triangleMaskLayer;
        view.tag = i;
        view.layer.masksToBounds = YES;
        [triangleWrapper addSubview:view];
        
        // Pan gesture recognizer
        UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(didPanOnCollectionView:)];
        gesture.minimumNumberOfTouches = 1;
        gesture.maximumNumberOfTouches = 1;
        [view addGestureRecognizer:gesture];
    }
    
    - (void)didPanOnCollectionView:(UIPanGestureRecognizer *)gesture {
    if (gesture.numberOfTouches > 0) {
        CGPoint panPoint = [gesture locationOfTouch:0 inView:self.collectionView];
        
        UIView *sender = gesture.view;
        NSLog(@"Panned over view with tag %li", (long)sender.tag);
    }
}
}