Leveraging UIPresentationController, this animation mimics the iOS Mail app's compose animation. This is intended as a code example, not a drag-n-drop library for use in a production Xcode project.
You can find the a great tutorial on UIPresentationController by Sam Davies here: https://www.shinobicontrols.com/blog/posts/2014/09/04/ios8-day-by-day-day-24-presentation-controllers
Source code for Sam Davies' presentation: https://github.com/ShinobiControls/iOS8-day-by-day
A very helpful video WWDC 2014 related to UIPresentationController, in general, is A Look Inside Presentation Controllers found here:
https://developer.apple.com/videos/wwdc/2014/
Source code for the WWDC 2014 presentation is: https://developer.apple.com/library/ios/samplecode/LookInside/LookInsidePresentationControllersAdaptivityandCustomAnimatorObjects.zip
Last but not least is our Stack Overflow conversation about this animation. If you have questions, please respond to this thread:
http://stackoverflow.com/questions/29017403/replicating-the-style-of-the-ios-mail-apps-compose-function/29040354?noredirect=1