How to add Custom View class in XCode 4 iOS Project?

I create a subclass of UIView named "WebViewContainer", In Interface Builder 3 ,we can drag the WebViewContainer to Ma开发者_如何学运维inViewController, but in xcode 4, I couldn't find that, in the "Custom Objects", it's empty:(

Drag a view object in to the window and change its default class to "WebViewContainer".

See this video on youtube http://www.youtube.com/watch?v=-u-Kdp-lYgM