UIView: Performance/memory difference between alpha:0, hidden:YES, removeViewFromSuperview and frame.origin.y = -100000;

Question

What is best for the device when temporarily hiding a view (e.g. until loading is done)?

• Setting alpha to 0?
• Setting hidden to YES?
• Removing view from superview?
• Moving the view to a position which makes it not possible to be visible on window/screen (e.g. frame.origin.y = -10000)?

Which is best in terms of memory and which is best in terms of performance? I know Apple somewhere wrote something about this, but I can't find it.

Answer 1

Which is best in terms of memory

removeFromSuperview is the best in term of memory. Why ? Because it will cause the view to be released. So if the view is not retained by anyone else (like a strong ivar), it will be deallocated.

And which is best in terms of performance?

setHidden: is the best in terms of performance. Why ? Because the action is just to set a flag. And then in drawRect it's just a BOOL check. So it's really fast because there is no other action involved.

Answer 2

So, the fastest method first:

1. setHidden (discard view from rendering only)
2. alpha to 0 is Equal to setHidden, but it first checks if0`
3. removeFromSuperView (need some steps: deallocate object, pop from stack (pointer), remove from rendering stack...)
4. frame.origin.y=-10000 > must move a whole bit array and check if the view comes out of bounds. not very fast...