Synthesize Qt Settings

Tags: , ,

I frequently create classes that I use as an interface to settings in my apps. Using a single class with accessors makes the code readable, safer and simple to maintain. Unfortunately, doing this requires to create getters and setters for every entry in the settings file, which is a bit bothering. Also, QSettings is not a QObject and cannot provide signals to notify changes.

My use cases are typically very simple, so I created a couple of macros that synthesise classes for me. Macros synthesise a reentrant class that can be used to access settings and a notifier, that can be used to get notifications of the changes. An example of definition of the class is:

L_DECLARE_SETTINGS(LSettingsTest, new QSettings("settings.ini", QSettings::IniFormat))
L_DEFINE_VALUE(QString, string1, QString("string1"), toString)
L_DEFINE_VALUE(QSize, size, QSize(100, 100), toSize)
L_DEFINE_VALUE(double, temperature, -1, toDouble)
L_DEFINE_VALUE(QByteArray, image, QByteArray(), toByteArray)
L_END_CLASS

L_DECLARE_SETTINGS(LSettingsTestSec1, new QSettings("settings.ini", QSettings::IniFormat), "SECTION_1")
L_DEFINE_VALUE(QString, string2, QString("string2"), toString)
L_END_CLASS

this will let you instantiate objects of class LSettingsTest and LSettingsTestSec1, and access entries with strong typed methods. Also, by calling LSettingsTest::notifier(), you can get a reference to the unique notifier. By setting an instance as a context property, you can get notifications and you can update settings from QML. You can find some more info in the repo https://github.com/carlonluca/lqtutils and an example using Qt Quick here: https://github.com/carlonluca/lqtutils/tree/master/LQtUtilsQuick.
Bye! ­čśë

Leave a Reply

Your email address will not be published.