Can a view be added to multiple other views safely, if so what does removeFromSuperView: do in that case?

Question

I am wondering what happens if a single instance of a UIView object gets added as a subview of multiple other views simultaneously. If UIView:removeFromSubview: gets called then does it get removed from all superviews or just the currently displayed one?

For background:

I have a status-bar like view object that needs to be displayed within several different other views (each other view is managed by its own view controller).

[i.e. a) the user is in one view, b) something happens to make the status-bar-like view appear, c) the user switches to another view d)the status bar is still visible in the new view e) the status bar expires after a time and disappears from site. And so on]

Initially I implemented this by adding/removing it as required as a subview of the window, and this was managed by a singleton. However due to some complications with some animations I have instead added it as a subview of each of the main view's for each of the view controllers. Note that there are not multiple copies

When the view needs to be removed I am calling its removeFromSuperview:, and everything is all working perfectly.

However I am wondering what the situation is regarding the removal of the view, is it being fully removed or is there something else I need to do?

For example the view might get added to N view controller's views by calling addSubview as required (it will only get added to each view controller if that view controller actually launches) However when it is being removed I am only calling removeFromSuperview: for the view of currently loaded view controller, not all view controllers it might have been added to.

Next time I navigate to one of these other view controllers it displays fine without the view being there, even though I didn't explicitly call removeFromSuperView.

As I said everything is working as it is, however at the back of my mind I feel there might be something missing?

Hope this was understandable.

Answer 1

You can only have it added to one view. Documentation is your friend!

• (void)addSubview:(UIView *)view: Views can have only one superview. If view already has a superview and that view is not the receiver, this method removes the previous superview before making the receiver its new superview.