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Suppose I have a UIView parentView and a subview childView that is rotated at some unknown angle relative to parentView. What is the most efficient way to determine if a point within parentView (I know the coordinates in parentView's coordinate system) is within a rectangle in childView's coordinate system (the rectangle is orthogonal to, but not equal to its bounds and probably not orthogonal to parentView's bounds)?
363
At its simplest, a view's bounds refers to its coordinates relative to its own space (as if the rest of your view hierarchy didn't exist), whereas its frame refers to its coordinates relative to its parent's space.
frame = a view's location and size using the parent view's coordinate system ( important for placing the view in the parent) bounds = a view's location and size using its own coordinate system (important for placing the view's content or subviews within itself)
Frame A view's frame ( CGRect ) is the position of its rectangle in the superview 's coordinate system. By default it starts at the top left. Bounds A view's bounds ( CGRect ) expresses a view rectangle in its own coordinate system.
The UIView class is a concrete class that you can instantiate and use to display a fixed background color. You can also subclass it to draw more sophisticated content.
Convert the point to the subview's coordinate system and then use CGRectContainsPoint:
CGPoint pointInSubview = [subview convertPoint:pointInSuperview fromView:superview];
if (CGRectContainsPoint(rectInSubview, pointInSubview)) {
NSLog(@"We have a winner!");
}
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