The Layout is also a very tricky part. On iOS the app is always in full screen. On OS X, there are infinite number of display sizes and the user can dynamically change the size and ratio of the window of your app.
Apple are pushing both iOS and Mac developers to use autolayout (especially on the iOS side), which is meant to solve some of these problems.
I say 'meant to' because autolayout is far from perfect, but there's a pretty clear shift on the iOS side from a "code to a fixed 320x480 window" to a "write a UI that can adapt to different sizes gracefully". For example, apps should in iOS 7 really now be able to handle varying text sizes (and thus layout) according to user preference.
I say 'meant to' because autolayout is far from perfect, but there's a pretty clear shift on the iOS side from a "code to a fixed 320x480 window" to a "write a UI that can adapt to different sizes gracefully". For example, apps should in iOS 7 really now be able to handle varying text sizes (and thus layout) according to user preference.