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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:
Person { name: "Bob Jones" shoeSize: 12 }
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.
#include <qdeclarative.h> 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; }; QML_DECLARE_TYPE(Person);
Following the class declaration, we include the QML_DECLARE_TYPE() macro. This is necessary to declare the type to QML. It also includes the logic necessary to expose the class to Qt's meta system - that is, it includes the Q_DECLARE_METATYPE() functionality.
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 implementation must also be registered using the QML_REGISTER_TYPE() macro. This macro registers the Person class with QML as a type in the People library version 1.0, and defines the mapping between the C++ and QML class names.
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.
Copyright © 2010 Nokia Corporation and/or its subsidiary(-ies) | Trademarks | Qt 4.7.0 |