Xcode Workspace vs Nested Projects

I use workspaces when I want to combine projects while also maintaining project independence.

An example where I use workspaces is series of tutorial projects that progress from very simple to more complex. Each project can function as a standalone project, but grouping them together in a workspace helps my organization of the overall project.

In another instance I have an app developed for a client. The app works as both a standalone app and a module in the overall project. The independent project can build the standalone app. The other app uses a workspace that includes two projects. The module version of the app is built from a special scheme, and this combined app doesn't build without using the workspace.

One twist with the two above situations is where the build folder is stored. I have to change the Xcode preference to put the build products into unique folders for the group of tutorial projects, use a common build folder for the module within the other app setup.

In other circumstances I have plenty of projects with embedded projects. In these situations the library projects are stable. I don't attempt further development of the library projects so they are just another resource for the project. I find it easier to work where my file system organization of project resources somewhat reflects the organization of my Xcode project. So these library projects are copied into the main project's file hierarchy. It would make sense to use workspaces if I was developing the libraries and using them in multiple projects. For expedience I frequently don't bother.

Sometimes I even combine workspaces with projects containing embedded projects.

So my opinion is that both organizational tools, embedded projects and workspaces, have their merits and problems. I choose to use one or the other (or a combination) depending upon the particular circumstances.

We added nested projects into the Main project's Frameworks, so we could "include" them into the .framework product.

Main|-- Main|-- MainTests|-- Frameworks|   |-- CommonLibrary.xcodeproj|   |-- AnotherCommonLibrary.xcodeproj|   |-- UIKit.framework|   |-- Foundation.framework|   |-- CoreFoundation.framework|-- Products

See this Great Tutorial by Jeff Verkoeyen for adding Universal Frameworks to a project. It not easy, at first, but keep working on it and you'll get the hang of it.