Cocoa iOS Make a Rectangle into a Circle with Collisions - objective-c

Question

So I have a UIView called fallingBall that currently collides nicely with my UIView called theBlockView. I am using CGRectIntersectsRect(theBlockView.frame, fallingBall.frame) to detect this collision.
That's all very well, so now I would like my fallingBall to actually be round, and I would also like the top corners of theBlockView to be rounded. To do this, I used the following code:
//round top right-hand corner of theBlockView
UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:theBlockView.bounds
byRoundingCorners:UIRectCornerTopRight
cornerRadii:CGSizeMake(10.0, 10.0)];
CAShapeLayer *maskLayer = [CAShapeLayer layer];
maskLayer.frame = theBlockView.bounds;
maskLayer.path = maskPath.CGPath;
theBlockView.layer.mask = maskLayer;
//round the fallingBall view
[[fallingBall layer] setCornerRadius:30];
But, funnily enough, though they look nice and rounded, the views are still rectangles.
So my question is: how can I make CGRectIntersectsRect treat them as the shapes that they look like? Is there a function that works the same but uses the view's alpha to detect collisions?
Thanks for your time!

Answer 1

Actually, let me answer my own question!
OK, so I spent the greater part of the last 10 hours looking around, and I came across this post: Circle-Rectangle collision detection (intersection) - check out what e.James has to say!
I wrote a function to help with this: first, declare the following structs:
typedef struct
{
CGFloat x; //center.x
CGFloat y; //center.y
CGFloat r; //radius
} Circle;
typedef struct
{
CGFloat x; //center.x
CGFloat y; //center.y
CGFloat width;
CGFloat height;
} MCRect;
Then add the following function:
-(BOOL)circle:(Circle)circle intersectsRect:(MCRect)rect
{
CGPoint circleDistance = CGPointMake(abs(circle.x - rect.x), abs(circle.y - rect.y) );
if (circleDistance.x > (rect.width/2 + circle.r)) { return false; }
if (circleDistance.y > (rect.height/2 + circle.r)) { return false; }
if (circleDistance.x <= (rect.width/2)) { return true; }
if (circleDistance.y <= (rect.height/2)) { return true; }
CGFloat cornerDistance_sq = pow((circleDistance.x - rect.width/2), 2) + pow((circleDistance.y - rect.height/2), 2);
return (cornerDistance_sq <= (pow(circle.r, 2)));
}
I hope this helps someone!

Answer 2

CGRectIntersectsRect will always use rectangles, also the frames of the views will always be rectangles. You will have to write your own function. You could use the center of your views to calculate circles using the corner radius, and test if the rectangles AND the circles intersect somehow.