Extending QML - Adding Types Example

Files:

• declarative/cppextensions/referenceexamples/adding/example.qml
• declarative/cppextensions/referenceexamples/adding/person.cpp
• declarative/cppextensions/referenceexamples/adding/person.h
• declarative/cppextensions/referenceexamples/adding/main.cpp
• declarative/cppextensions/referenceexamples/adding/adding.pro
• declarative/cppextensions/referenceexamples/adding/adding.qrc

The Adding Types Example shows how to add a new element type, Person, to QML.

The Person type can be used from QML like this:

 import People 1.0

 Person {
     name: "Bob Jones"
     shoeSize: 12
 }

Declare the Person class

All QML elements map to C++ types. Here we declare a basic C++ Person class with the two properties we want accessible on the QML type - name and shoeSize. Although in this example we use the same name for the C++ class as the QML element, the C++ class can be named differently, or appear in a namespace.

 class Person : public QObject
 {
     Q_OBJECT
     Q_PROPERTY(QString name READ name WRITE setName)
     Q_PROPERTY(int shoeSize READ shoeSize WRITE setShoeSize)
 public:
     Person(QObject *parent = 0);

     QString name() const;
     void setName(const QString &);

     int shoeSize() const;
     void setShoeSize(int);

 private:
     QString m_name;
     int m_shoeSize;
 };

Define the Person class

 Person::Person(QObject *parent)
 : QObject(parent), m_shoeSize(0)
 {
 }

 QString Person::name() const
 {
     return m_name;
 }

 void Person::setName(const QString &n)
 {
     m_name = n;
 }

 int Person::shoeSize() const
 {
     return m_shoeSize;
 }

 void Person::setShoeSize(int s)
 {
     m_shoeSize = s;
 }

The Person class implementation is quite basic. The property accessors simply return members of the object instance.

The main.cpp file also calls the qmlRegisterType() function to register the Person type with QML as a type in the People library version 1.0, and defines the mapping between the C++ and QML class names.

Running the example

The main.cpp file in the example includes a simple shell application that loads and runs the QML snippet shown at the beginning of this page.