When does UIKit remove constraints automatically

Question

In my updateLayoutConstraints, I am adding constraints, and then I call super.updateLayoutConstraints(). According to the Apple documentation, this seems OK, however does UIKit remove constraints automatically before calling this function?

I am finding that this works OK but I am concerned that I am just re-adding the same type of constraints.

When does UIKit remove constraints automatically or doesn't it?

Answer 1

No updateConstraints does not remove any constraints you added. If you want to avoid adding duplicate constraints, you need to set a flag or keep references to the constraints you already created.