使用WillSet属性观察器更改值

Question

I am attempting to create a UIView subclass. In the initialization, I set minimum and maximum y-axis origin values I want the subclass to have. This view will be moved up and down programmatically, by user gestures or through an animation. I was hoping I could use the willSet property user for this:

override var frame: CGRect {
    willSet {
        if newValue.origin.y > maximumOriginY {
            self.frame.origin.y = maximumOriginY
        }
        if newValue.origin.y < minimumOriginY {
            self.frame.origin.y = minimumOriginY
        }
    }
}

However, it doesn't seem to do anything. I have tried using DidSet property observer, but this resets the origin after it has been set, resulting in a stutter animation. Any ideas on how to get this to work with property observers or another way? Thanks

Answer 1

it is not possible to change the values within the willSet observer. overriding the getter and setter could work:

override var frame: CGRect {
    get { return super.frame }
    set {
        var tempFrame = newValue
        tempFrame.origin.y = min(max(tempFrame.origin.y, minimumOriginY), maximumOriginY)
        super.frame = tempFrame
    }
}