如何在Xcode中为UIView的宽度和高度设置动画？

I have this subview I want to add to my main view, but make it expand from the origin. I read some of the Apple documentation but I don't understand where I am making mistake. I can animate the origin of the frame, i.e. to get it slide in from wherever, but the width/height doesn't seem to animate. Code as follows:I have this subview I want to add to my main vi