I\'m testing this and it appears that if you change the value within didSet, you do not get another call to didSet.
var x: Int = 0
It'll work just fine, but it seems pretty like a pretty bad idea from the standpoint of a consumer of your API.
It doesn't recurse, the way I suspected it might, so that's good at least.
I can think of few cases in which it would be acceptable for a setter to change what i'm setting. One such example might be a variable that's set to an angle, which is automatically normalized to be [0, 2π].