QScriptable Class

Detailed Description

With QScriptEngine::newQObject(), you can expose the signals and slots and properties of any QObject (or subclass) to script code. QScriptable augments this functionality by giving your C++ members access to the Qt Script environment they are invoked in; conceptually, it is similar to QObject::sender().

By subclassing QScriptable, you get the following functions in your class: thisObject(), argumentCount(), argument(), context() and engine(). With these functions, you have full access to the Qt Script environment from the slots and property access functions of your class, when they are invoked from script code.

For example, you can throw a Qt Script exception from a slot; manipulate the `this' object associated with the function call; inspect the arguments stored in the QScriptContext to know the "real" arguments passed to the function from script code; and call script functions from your slot.

A typical use case of QScriptable is to implement prototype objects for custom C++ types. You define the scriptable interface of your custom type in a QScriptable subclass using properties and slots; then you wrap an instance of your class using QScriptEngine::newQObject(), and finally pass the result to QScriptEngine::setDefaultPrototype(). See the Default Prototypes Example to see how this can be done.

The following is what subclassing QScriptable typically looks like:

 class MyScriptableObject: public QObject,
       protected QScriptable
 {
     Q_OBJECT
 ...

 public slots:
     void doSomething();
     double doSomethingElse();
 }

The only difference from regular QObject subclassing is that you also inherit from QScriptable.

In the implementation of your slots, you can then use the functions inherited from QScriptable:

 void MyScriptableObject::doSomething()
 {
   context()->throwError("Threw an error from a slot");
 }

 double MyScriptableObject::doSomethingElse()
 {
   return qscriptvalue_cast<double>(thisObject());
 }