Question

I have a class file (header and cpp) that I made, that I want to use in my main.cpp file. I generated a qmake project file (from the current directory of my main.cpp) and added the header and cpp with:

HEADERS += $$quote(/home/myusername/projects/src/myclass.h)
SOURCES += $$quote(/home/myusername/projects/src/myclass.cpp)
SOURCES += main.cpp

when I run the makefile, it seems to work until it gets to the part of my main.cpp where i include the header file and then it says: fatal error, no such file or directory

I feel like i’m making a really basic mistake, but I can’t seem to figure it out.

Answer 1

First, using absolute paths in a project file is definitely a bad idea.

If that class is a part of the project, but is located in another directory, use relative paths both in the project file and in the #include directive, using #include "relative/path/myclass.h" syntax.

If that class is not a part of the project, then you should compile it as a library, then use qmake with the following options:

qmake INCLUDEPATH+=/path/to/the/header LIBS+=-L/path/to/the/library

And add the library name to the project file:

LIBS += -llibraryname

Then you may include your class as #include <myclass.h>, note the <> syntax.

Note that workstation-specific things go to the command line, but the workstation-independent library name goes to the project file. If you want to provide some sensible default location, you could use the following trick:

unix { # default path for the Unix systems
  isEmpty(MYLIB_PATH): MYLIB_PATH = /usr/local
}
INCLUDEPATH += $$MYLIB_PATH/include
LIBS += -L$$MYLIB_PATH/lib

Then, if you want, you can still override the path from the command line:

qmake MYLIB_PATH=/home/myusername/mylib