Interfaces between C++ and QML Code in Qt Positioning
Depending on the type of C++ class QtPositioning utilizes two methods to simplify exchange of position data between C++ and QML code.
Starting with Qt 5.5, it has become much easier to integrate non-QObject based data types into QML. This is achieved by adding Q_GADGET support to QtQml. The macro converts classes into a light-weight version of a QObject without the required QObject inheritance. At the same time it retains the reflection capabilities of QMetaObject. As a result they can be directly exposed to QML and do not require any further wrapper classes.
A significant number of Position and Location related data types were converted to Q_GADGETs. They retain their API and value type character but have become introspectable via QMetaObject. This conversion was done to the following classes:
Using QGeoCoordinate as an example, the C++ types are directly exposed to the QML environment via its meta type:
The Address.address property is used to provide an interface between C++ and QML code. First a pointer to a Address object must be obtained from C++, then use the property() and setProperty() functions to get and set the
address property. The following gets the QGeoAddress representing this object from C++:
The following sets the properties of this object based on a QGeoAddress object from C++:
The Location.location property is used to provide an interface between C++ and QML code. First a pointer to a Location object must be obtained from C++, then use the property() and setProperty() functions to get and set the
location property. The following gets the QGeoLocation representing this object from C++:
The following sets the properties of this object based on a QGeoLocation object from C++:
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