I currently have the iOS 7 library and plan to upgrade my library to iOS 8. I would like to know what the impact of this update will be on the projects I already own.
Will I be able to support my iOS 7 projects without any problems?
Reason for my question is that when I was upgrading from iOS 6 to iOS 7, there was a huge impact. I had to redo most of the canvases of my projects. It ended up generating a lot of rework and injury.
It's hard to say if you'll have problems or not, this will vary from the components and dependencies of each project.
You can check the list of changes directly in the Apple documentation: link
The change was not as drastic as iOS 6 to iOS 7 . Some that I can rate for you are:
UIAlertController that came to replace UIAlertView and UIActionSheet . WKWebView substituting UIWebView . If you want to submit an application in the store you are required to support the Apple SDK8 and consecutively the new iOS8. You should not start having so many problems, but there are certain features that have been changed that will still require some work.