How to include multiple Xcode projects in a master project

Question

I recently asked about the wisdom of using multiple Xcode projects to separate project components. I have decided to follow this route in my next project.

I attempt

Answer 1

Project -> Edit Project Settings

Use Header Search Paths

This is a list of paths to folders to be searched by the compiler for included or imported user header files (those headers listed in quotes) when compiling C, Objective-C, C++, or Objective-C++. Paths are delimited by whitespace, so any paths with spaces in them need to be properly quoted. See the description of the Always Search User Paths build setting for more details on how this setting is used. If the compiler doesn't support the concept of user headers, then the search paths are prepended to the any existing header search paths defined in Header Search Paths. [USER_HEADER_SEARCH_PATHS, -iquote]