Is it a good practice to have more than one *.xcodeproj file in an xCode project?

I want to know what's the best practice to use when integrating external SDK to my project, specifically how to handle the *.a file and the *.xcodep开发者_如何转开发roj file.

Examples of external SDK packages: PhoneGap, Facebook, Google-Analytic.

Is there a reason to copy the *.xcodeproj to my existing project or is it enough to just use the *.a file?

Are there pros and cons for having more than one *.xcodeproj file in a single project?

You would never copy the .xcodeproj into your app.

Typically you would add the library (./a) or any headers and implementation files required (.h & .m).

Often you would compile the 3rd party SDK xcode project to a library file and include that compiled library file.