Swift - making buttons and labels appear and disappear

What I want to know:

I want to know that how to make buttons/labels appear and disappear. When my character collides with an object the buttons/labels will show up over the view and the game-view wont be working any more, only the buttons/labels that appeared can be interacted with.

What I have tried:

I have tried .hidden = false and .hidden = true but it didn't work but maybe I was not using it correctly.

NOTE:

No code is needed for this as I just need to know an explanation and how to do it.