In Delphi, should I add shared units to my projects, to a shared package, or neither?

Question

This question is similar to this one, but not a duplicate because I'm asking about issues not discussed in that question.

I have a client-server project in Delphi 7 with the following directory structure:

\MyApp
  \MyClientApp
  \MyServerApp
  \lib

There are 2 actual Delphi projects (.dpr), one each in the MyClientApp and MyServerApp folders.

The lib folder has .pas units that have common code to the client and server apps. What I'm wondering is if I should include those .pas files in the client and server projects? Or should I create a package in the lib folder which includes those units? Or should I just leave the .pas files sitting in the lib folder and not add them to any app/package?

What are the pros/cons of each approach? Which way is "best"? Is there any issue with having those units from the lib folder be included in more than one project?

Right now the units in the lib folder are not a part of any app/package. One disadvantage of this is that when I have my client app open in Delphi, for example, and I want to search in all files in the project for something, it doesn't also search in the units in the lib folder. I get around this by opening those units and doing a find in all open files, or using grep search (but I'd prefer a better solution).

I would also greatly prefer a solution where I will not have to go and open some separate package and recompile it when I make changes to those files in the lib folder (is this where I should use a project group?).

Answer 1

Sharing units between applications always carries the risk of incompatible changes done in one application that breaks the other. On the other hand, making copies of these units is even worse, so your approcach of moving them to their own subdirectory at least adds a psychological barrier to changing them without considering other programs.

As for adding them to the project files: I usually add some units which I frequently access (either for expanding or for reference) from the IDE to the project, and leave others out for the compiler to pick using the search path. I do that on per project basis, that means, some units may be part of several projects, why not?

Putting them into a package only makes sense, if you actually want to create a package based application, otherwise, why bother?

For more info on how I organize my projects and libraries, see http://www.dummzeuch.de/delphi/subversion/english.html