Use a library

If you want to go further into the creation of the project, we can also create a QML library.

Libraries can be used to shared QML widgets between multiple apps. We will see how later in the course.

Create target

When you build a QML library in cmake, you have to use qt_add_library instead of add_library.

This cmake function takes the same parameters as the original function.

Add qml

In order to add qml files, we will need to use a new function: qt_add_qml_module.

We will no go through all the parameters so here is the doc.

Here are the parameters for a minimal case:

qt_add_qml_module(${_libName}
    URI ${_libName}
    QML_FILES ${_qmlFiles}
    RESOURCES ${_qmlResources}
    NO_PLUGIN)

• The first parameter is the name of the target
• URI is the name that will be used to import the widgets into the qml
• QML_FILES is a list of qml files
• RESOURCES is a list of resources like icons for examples. These will be accessible via the qt resource manager ( (more on that on a later chapter))

By default, for a library, the qt_add_qml_module will create another target named myLibplugin (if the original lib is names myLib) (see doc)

The original target will contain all the source code and the plugin target will contains the qml import logic, so that the widgets from the lib can be used in the app.

Link to app

If you only want to use the cpp files, you have to link the original library (ex: myLib). But if you also want to use the qml, you will have to also link the plugin library (ex: myLibplugin).

This can be a bit of a bother when you plan to always use them both. That is why we can add the NO_PLUGIN parameters. This will merge both targets, allowing you to only link the original target.

And finally, you can import the library into the qml using import myLib

set(_libName uiLib)

set(_qmlFiles
    widgets/Hello.qml
    widgets/SimpleIcon.qml)

set(_qmlResources
    assets/icon.svg)

set(_publicLinks
    Qt::Core
    Qt::Qml
    Qt::Quick
    Qt::Widgets)

qt_add_library(${_libName} STATIC)

qt_add_qml_module(${_libName}
    URI ${_libName}
    QML_FILES ${_qmlFiles}
    RESOURCES ${_qmlResources}
    NO_PLUGIN)

target_link_libraries(${_libName} PUBLIC ${_publicLinks})

import uiLib

ApplicationWindow {
    id: root

    ...

    Hello {}
}