Is it possible to include a library from another library using the Arduino IDE?

Question

I'm trying to write an Arduino library (effectively a C++ class) which itself references another library I have installed in my Mac's ~/Documents/Arduino/libraries directory.

At the top of the .cpp of the library I'm writing, I've tried

#include <ReferencedLibrary.h>

and

#include "ReferencedLibrary.h"

... neither of which work. I can successfully #include <ReferencedLibrary.h> from sketches in my ~/Documents/Arduino directory. Am I missing something or is this a limitation of the Arduino IDE/makefile? Is there a workaround?

Answer 1

I have been able to include a library in another Arduino library by using a relative path. For example, to include the AbstractSwitch library into the DigitalSwitch library, assuming that both of these libraries live in their own separate folders within Arduino's standard library folder, you can use the following include statement:

#include "../AbstractSwitch/AbstractSwitch.h"

In other words, your include statement should read:

#include "../LibraryFolder/LibraryHeaderFile.h"

Answer 2

The documentation here https://github.com/arduino/Arduino/wiki/Build-Process states:

The include path includes the sketch's directory, the target directory (/hardware/core//) and the avr include directory (/hardware/tools/avr/avr/include/), as well as any library directories (in /hardware/libraries/) which contain a header file which is included by the main sketch file.

This means that if you #include "ReferencedLibrary.h" from your main sketch file, this causes that file's libraries directory to get added to the include path for other libraries to include. A bit of a hack but it does work on my Mac.