如何将UIView置于自定义控件中？

I'm working on a exercise to create a custom control of anything. My idea is to have a UIView in the middle of the screen and a UILabel below it. When you tap on the view a random color will appear with the label changing to its hex value. When trying to create this custom control I'm having a problem trying to center the UIView programmatically. I get to an issue at `colorBox.center~I'm working on a exercise to create a custom co