visual c++: #include files from other projects in

Question

I am working on a game using Visual C++. I have some components in separate projects, and have set the project dependencies. How do I #include a header file from a different project? I have no idea how to use classes from one project in another.

Answer 1

You need to set the path to the headers in the project properties so the compiler looks there when trying to find the header file(s). I can't remember the exact location, but look though the Project properties and you should see it.

Answer 2

Try to avoid complete path references in the #include directive, whether they are absolute or relative. Instead, add the location of the other project's include folder in your project settings. Use only subfolders in path references when necessary. That way, it is easier to move things around without having to update your code.

Answer 3

#include has nothing to do with projects - it just tells the preprocessor "put the contents of the header file here". If you give it a path that points to the correct location (can be a relative path, like ../your_file.h) it will be included correctly.

You will, however, have to learn about libraries (static/dynamic libraries) in order to make such projects link properly - but that's another question.

Answer 4

Settings for compiler

In the project where you want to #include the header file from another project, you will need to add the path of the header file into the Additional Include Directories section in the project configuration.

To access the project configuration:

1. Right-click on the project, and select Properties.
2. Select Configuration Properties->C/C++->General.
3. Set the path under Additional Include Directories.

How to include

To include the header file, simply write the following in your code:

#include "filename.h"

Note that you don't need to specify the path here, because you include the directory in the Additional Include Directories already, so Visual Studio will know where to look for it.

If you don't want to add every header file location in the project settings, you could just include a directory up to a point, and then #include relative to that point:

// In project settings
Additional Include Directories    ..\..\libroot

// In code
#include "lib1/lib1.h"    // path is relative to libroot
#include "lib2/lib2.h"    // path is relative to libroot

Setting for linker

If using static libraries (i.e. .lib file), you will also need to add the library to the linker input, so that at linkage time the symbols can be linked against (otherwise you'll get an unresolved symbol):

1. Right-click on the project, and select Properties.
2. Select Configuration Properties->Linker->Input
3. Enter the library under Additional Dependencies.