What is the relationship between a UIView's frame origin and its center?

Question

Say I'm creating an animation, and I want to move the center of a UIView to a certain CGPoint I have. I know what I want the center to be, just the aforementioned CGPoint , and I know the width and height that I want, but when I go to create the frame for my UIView I have no idea what to set for the x and y for the origin .

Should I just be setting 0, 0 or anything really? Does it matter?

Should I just be thinking as setting center as a different method of setting the origin? Makes me wish CGRect had an instantiator with center as an option.

There has been a previous question addressing a somewhat similar question, but it addresses them as three separate entities, rather than how to deal with center when creating the view.

Answer 1

Yes, go ahead and set the initial frame's origin to anything, since subsequently setting the center will effectively move this origin anyway. It is not uncommon to initialise views with a frame of CGRectZero when it is going to be fully configured later.

frame is actually just a calculated property based on the view's center and bounds , and so all three are intrinsically linked when it comes to view layout. The UIView Class Reference has this to say about it:

The geometry of a view is defined by its frame , bounds , and center properties. The frame defines the origin and dimensions of the view in the coordinate system of its superview and is commonly used during layout to adjust the size or position of the view. The center property can be used to adjust the position of the view without changing its size. The bounds defines the internal dimensions of the view as it sees them and is used almost exclusively in custom drawing code. The size portion of the frame and bounds rectangles are coupled together so that changing the size of either rectangle updates the size of both.