使用autolayout设置动态UIView以匹配容器视图

I have a UIView in IB that has another UIView within it, which I am using as a container view. In code, I create three different views and then animate the appropriate one into the container's view depending on the state of the app. Only one of the three different views will be valid at any given time. The problem is, when I run on different iPhone's in the simulator, my new subviews are not scaled to match the container view. I am using autolayout. For testing purposes, I've set up my subviews to just be a big button that has all it's edges constrained to the superview. And the container view also has it's edges constrained to it's superview. What I want is for the subview to match the container's view. i.e the button stretches the entire size of the container view. When run on different iPhones the size of the container view and therefore the subview should scale proportionally relative to the different iPhone's screen sizes.I have a UIView in IB that has another UIView w