How to use QMake's subdirs template?

Question

Hi,
I'm starting to learn Qt. I'm moving from the Visual Studio world and I am looking for a way to organize my project's structure using QMake. I've found the 'subdirs' template but I have quite a hard time understanding it.

My project structure looks like this:

project_dir/
    main.cpp
    project.pro
    logic/
      logic.pro
      some logic files
    gui/
      gui.pro
      gui files

My project.pro looks like this

TEMPLATE = subdirs
SUBDIRS = logic \
          gui
SOURCES += main.cpp

In the .pro files for the subdirectories I have appropriate SOURCES, HEADERS and RESOURCES variables set.

Please tell me what TARGET, TEMPLATE and other necessary values I should set in the .pro files.

Also, is there some good QMake tutorial other than the official one?

Answer 1

You use subdirs if the logic and gui folders actually repesent some sort of target, eg. a library, that can be built independently of anything else. If that's the case then just use

TEMPLATE = lib
TARGET = logic
CONFIG += dll

in logic.pro.

If they are not independent targets but are just folders that exist to organise the sources files then you can just use a .pri file in each instead and include them within the .pro using

include(logic/logic.pri)
include(gui/gui.pri)

Just remember that the file paths in the .pri files are relative to the .pro file and not the .pri. BTW, the use of a .pri file is optional as you can still list the files in those folders directly in the .pro file. The .pri file just makes it that bit neater and helps keep the .pro file shorter.

Answer 2

In addition to Troubadour's comment, I would note that the SUBDIRS target is only good for specifying subdirectories. Therefore, your extra line of

SOURCES += main.cpp

in your project.pro file is incorrect, and will likely fail to build your main.cpp file, at worst. At best, qmake will refuse to parse the file, since it has conflicting specifications in it.

I've used the SUBDIRS template a few times, and it does well if you can build parts into more-or-less independent libraries, apparently like you have with the logic and the gui separate. Here is one way to do this:

project_dir/
-project.pro
-common.pri
-logic/
----logic.pro
----some logic files
-gui/
----gui.pro
----gui files
-build/
----build.pro
----main.cpp

project.pro:

TEMPLATE = subdirs
SUBDIRS = logic \
          gui

# build must be last:
CONFIG += ordered
SUBDIRS += build

common.pri:

#Includes common configuration for all subdirectory .pro files.
INCLUDEPATH += . ..
WARNINGS += -Wall

TEMPLATE = lib

# The following keeps the generated files at least somewhat separate 
# from the source files.
UI_DIR = uics
MOC_DIR = mocs
OBJECTS_DIR = objs

logic/logic.pro:

! include( ../common.pri ) {
    error( Couldn't find the common.pri file! )
}

HEADERS += logic.h
SOURCES += logic.cpp

# By default, TARGET is the same as the directory, so it will make 
# liblogic.a (in linux).  Uncomment to override.
# TARGET = target

gui/gui.pro:

! include( ../common.pri ) {
    error( Couldn't find the common.pri file! )
}

FORMS += gui.ui
HEADERS += gui.h
SOURCES += gui.cpp

# By default, TARGET is the same as the directory, so it will make 
# libgui.a (in linux).  Uncomment to override.
# TARGET = target

build/build.pro:

TEMPLATE = app

SOURCES += main.cpp

LIBS += -L../logic -L../gui -llogic -lgui

# Will build the final executable in the main project directory.
TARGET = ../project