Using an external .json file for configuration

[Clone45]

Hello! I'm working on an application where I want to load a json configuration file on startup. End users should be able to edit this json file and have the updated configuration loaded on startup as well.

When I first attempted this, I treated the json file as a resource. But... as I've been reading more about Qt resources, perhaps this isn't the right approach.

Let me restate my goals:

• When the application starts, I'd like it to load an external file named node_types.json
• node_types.json should be editable by end users if they so feel inclined. (This might be rare, but it should be possible.)
• When node_types.json is edited, the next time the application starts, it should load the new node_types.json file.
• Currently, node_types.json is stored in the project directory, in a folder called /res. I'm open minded about changing this location, as long as it is compatible with both Mac and PC

Thanks so much for any recommendations! I'm very new to Qt and have gotten pretty far with ChatGPT's help, but this feature has been difficult to perfect. If I treat node_types.json as a resource, it doesn't seem to get updated when I make changes to it.

Cheers,
Bret

[jsulm]

@Clone45 You should use https://doc.qt.io/qt-6/qstandardpaths.html#locate with QStandardPaths::AppConfigLocation to find the location for configuration of your application in a platform independent way. Then put your json file from res there if it is not yet done.

[Clone45]

@jsulm Thanks! I'll give that a shot!

[Clone45]

@jsulm I've run into some additional issues:

18:40:28: Starting C:\Users\clone\Documents\build-TinyBonsai-Desktop_Qt_6_5_0_MinGW_64_bit-Debug\TinyBonsai.exe...
Resource files:
":/qpdf"
":/qt-project.org"
Config file path: "C:/Users/clone/Documents/build-TinyBonsai-Desktop_Qt_6_5_0_MinGW_64_bit-Debug/module_types.json"
Could not copy file from ":/res/module_types.json" to "C:/Users/clone/AppData/Local/TinyBonsai\module_types.json"
Error: "Cannot open :/res/module_types.json for input"

I'm having trouble with my source resource file not being found. I've spent some time trying to figure this out on my own, but a little bit of advice would go a long way!

[jsulm]

@Clone45 Please show your res file and how you're trying to copy it.

[Clone45]

@jsulm Thanks so much for sticking with me.

Here is my resources.qrc file:

<RCC>
    <qresource prefix="/">
        <file>res/module_types.json</file>
    </qresource>
</RCC>

Here is my make CMakeLists.txt file:

cmake_minimum_required(VERSION 3.5)

project(TinyBonsai VERSION 0.1 LANGUAGES CXX)

find_package(Qt6 COMPONENTS Core Widgets REQUIRED)
qt6_add_resources(RESOURCE_FILES resources.qrc)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)

set(PROJECT_SOURCES
        main.cpp
        mainwindow.cpp
        mainwindow.h
        mainwindow.ui
        ModulesListModel.h
        module.h
        module.cpp
        moduletypes.h
        moduletypes.cpp
        moduletypesmanager.h
        moduletypesmanager.cpp
        nodecanvas.h
        nodecanvas.cpp
        port.h
        port.cpp
        defines.h
        connection.h
        connection.cpp
)

if(${QT_VERSION_MAJOR} GREATER_EQUAL 6)
    qt_add_executable(TinyBonsai
        MANUAL_FINALIZATION
        ${PROJECT_SOURCES}
    )
# Define target properties for Android with Qt 6 as:
#    set_property(TARGET TinyBonsai APPEND PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
#                 ${CMAKE_CURRENT_SOURCE_DIR}/android)
# For more information, see https://doc.qt.io/qt-6/qt-add-executable.html#target-creation
else()
    if(ANDROID)
        add_library(TinyBonsai SHARED
            ${PROJECT_SOURCES}
        )
# Define properties for Android with Qt 5 after find_package() calls as:
#    set(ANDROID_PACKAGE_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/android")
    else()
        add_executable(TinyBonsai
            ${PROJECT_SOURCES}
        )
    endif()
endif()

target_include_directories(TinyBonsai PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})

target_link_libraries(TinyBonsai PRIVATE Qt${QT_VERSION_MAJOR}::Widgets)

set_target_properties(TinyBonsai PROPERTIES
    MACOSX_BUNDLE_GUI_IDENTIFIER my.example.com
    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    MACOSX_BUNDLE TRUE
    WIN32_EXECUTABLE TRUE
)

install(TARGETS TinyBonsai
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})

if(QT_VERSION_MAJOR EQUAL 6)
    qt_finalize_executable(TinyBonsai)
endif()

And here's the code that I'm working with:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    // This is not compiling:
    // Q_INIT_RESOURCE(resources);

    // List all resource files
    QDir resourceDir(":/");
    QStringList resourceFiles = resourceDir.entryList();

    qDebug() << "Resource files:";
    for (const QString &fileName : resourceFiles) 
    {
        QFileInfo fileInfo(":/"+fileName);
        qDebug() << fileInfo.absoluteFilePath();
    }

    // Fist thing, copy the configuration file to the config location if it doesn't exist
    QString configFileName = "module_types.json";
    QString configFilePath = QStandardPaths::locate(QStandardPaths::AppConfigLocation, configFileName);

    qDebug() << "Config file path: " << configFilePath;
    
    QString sourceFilePath = ":/res/" + configFileName;
    QString targetDirectory = QStandardPaths::writableLocation(QStandardPaths::AppConfigLocation);

    // Create the target directory if it doesn't exist
    QDir dir;
    if (!dir.exists(targetDirectory)) {
        dir.mkpath(targetDirectory); // Create the target directory if it does not exist
    }

Ah, and here's where the configuration file is that I wish to copy.

[Christian Ehrlicher]

@Clone45 said in Using an external .json file for configuration:

qt6_add_resources(RESOURCE_FILES resources.qrc)

What should this do?

https://doc.qt.io/qt-6/qt-add-resources.html#examples

[Clone45]

@Christian-Ehrlicher Sorry Christian, I'm not quite following you. What I'm trying to achieve is include an external .json file along with my application which will be loaded by the application when it runs. The json file should be editable by the users.

It's completely possible that I'm going down the wrong path? It looks like qt_add_resources adds an external data file to the executable, but that doesn't seem to match my needs.

Any advice will be much appreciated!

[Christian Ehrlicher]

@Clone45 said in Using an external .json file for configuration:

? It looks like qt_add_resources adds an external data file to the executable, but that doesn't seem to match my needs.

It does exactly what you want but you're using it wrong. The link I gave you shows the correct usage. You should add RESOURCE_FILES somewhere as explained there.

[Clone45]

@Christian-Ehrlicher Apologies Christian. I appreciate the help.

I have the following in my CMakeLists.txt file:

cmake_minimum_required(VERSION 3.5)

project(TinyBonsai VERSION 0.1 LANGUAGES CXX)

find_package(Qt6 COMPONENTS Core Widgets REQUIRED)

#
#  Here's where I have added the resource files:
#    ↓↓↓↓
qt6_add_resources(RESOURCE_FILES resources.qrc) 

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

Is that what you're referring to? Is so, that's already in place, but I'm still having issues.

[Christian Ehrlicher]

@Christian-Ehrlicher said in Using an external .json file for configuration:

You should add RESOURCE_FILES somewhere as explained there.

Why don't yiu just follow the documentation and add the output of qt_add_resources() to qt_add_executable() as written in the example?

qt_add_executable(TinyBonsai MANUAL_FINALIZATION ${PROJECT_SOURCES} ${RESOURCE_FILES } )

How should cmake know otherwise where to add the generated file to?

[Clone45]

@Christian-Ehrlicher said in Using an external .json file for configuration:

@Christian-Ehrlicher said in Using an external .json file for configuration:

You should add RESOURCE_FILES somewhere as explained there.

Why don't yiu just follow the documentation and add the output of qt_add_resources() to qt_add_executable() as written in the example?
qt_add_executable(TinyBonsai MANUAL_FINALIZATION ${PROJECT_SOURCES} ${RESOURCE_FILES } )
How should cmake know otherwise where to add the generated file to?

Thank you for all of your help. It's working now, after I added the resource files to qt_add_executable. I had a little bit of trouble with overwriting the configuration file because of permissions issues, but I was able to work around that by setting the permissions explicitly in the code.

Cheers,
Bret

[Christian Ehrlicher]

@Clone45 said in Using an external .json file for configuration:

after I added the resource files to qt_add_executable

set(CMAKE_AUTORCC ON)

Yes, this is also possible because you enabled AUTORCC.