I used to do my global imports (i.e. imports that would be visible to all source files in my Xcode project) in the file AppName-prefix.pch
You can creTe your own, but the point really is that you shouldn't have global dependencies, you should explicitly import only what is required into each class. Indeed, in your .h files you should endeavour to use @class for everything and only import into your .m file. This approach makes the dependencies of a class very clear and reduces the likelihood of dependency circularities, which are both very good things.