How to combine 2 iOS navigation-based apps?

I currently have two navigation-based apps, call them MainApp and SecondApp. I'd like to put the SecondApp within the MainApp. Both apps compiled and ran on my computer. However, when I copy the SecondApp's class files into the MainApp it won't compile. Is there a more elegant way of doing this, or at least a way that actually works?

They error I'm getting is: "The run destination My Mac 64-bit is not valid for RUnning the scheme..." Which is weird be开发者_运维问答cause BOTH apps ran on my computer prior to their merging.

EDIT: problem solved by created a new scheme (Product > New Scheme...).

You're trying to Use Mac OS as the target. You should select an iOS version in the schemes drop down instead. This sometimes happens to me, and seems to be a bug in XCode 4.

If the option isn't in the schemes dropdown, see this link for how to fix it: Xcode 4: My iPhone projects have become Mac OS projects.. and I can't change this