Is there a way to lock the iPhone's screen orientation programmatically? Just like the Pocket app provides a lock button every time when the screen orientation changes, and the user can click the lock button to lock the screen orientation. I wonder how to implement a feature like this.

I searched the web and found these 2 related posts, but still can't find the solution.

http://forums.macrumors.com/showthread.php?t=1579703

http://www.quora.com/Is-Pockets-screen-orientation-lock-patented-Why-dont-other-apps-OSes-have-it

Thanks in advance.