Qt 4.8: Extending QML - Adding Types Example

Qt Reference Documentation

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# 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.