QMetaMethod Class Reference
[QtCore module]

bool QMetaMethod::invoke ( QObject * object, Qt::ConnectionType connectionType, QGenericReturnArgument returnValue, QGenericArgument val0 = QGenericArgument( 0 ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument() ) const

Invokes this method on the object object. Returns true if the member could be invoked. Returns false if there is no such member or the parameters did not match.

The invocation can be either synchronous or asynchronous, depending on the connectionType:

• If connectionType is Qt::DirectConnection, the member will be invoked immediately.
• If connectionType is Qt::QueuedConnection, a QEvent will be posted and the member is invoked as soon as the application enters the main event loop.
• If connectionType is Qt::AutoConnection, the member is invoked synchronously if object lives in the same thread as the caller; otherwise it will invoke the member asynchronously.

The return value of this method call is placed in returnValue. If the invocation is asynchronous, the return value cannot be evaluated. You can pass up to ten arguments (val0, val1, val2, val3, val4, val5, val6, val7, val8, and val9) to this method call.

QGenericArgument and QGenericReturnArgument are internal helper classes. Because signals and slots can be dynamically invoked, you must enclose the arguments using the Q_ARG() and Q_RETURN_ARG() macros. Q_ARG() takes a type name and a const reference of that type; Q_RETURN_ARG() takes a type name and a non-const reference.

To asynchronously invoke the animateClick() slot on a QPushButton:

 int methodIndex = pushButton->metaObject()->indexOfMethod("animateClick()");
 QMetaMethod method = metaObject->method(methodIndex);
 method.invoke(pushButton, Qt::QueuedConnection);

With asynchronous method invocations, the parameters must be of types that are known to Qt's meta-object system, because Qt needs to copy the arguments to store them in an event behind the scenes. If you try to use a queued connection and get the error message

 QMetaMethod::invoke: Unable to handle unregistered datatype 'MyType'

call qRegisterMetaType() to register the data type before you call QMetaMethod::invoke().

To synchronously invoke the compute(QString, int, double) slot on some arbitrary object obj retrieve its return value:

 QString retVal;
 QByteArray normalizedSignature = QMetaObject::normalizedSignature("compute(QString, int, double)");
 int methodIndex = obj->metaObject()->indexOfMethod(normalizedSignature);
 QMetaMethod method = metaObject->method(methodIndex);
 method.invoke(obj,
               Qt::DirectConnection,
               Q_RETURN_ARG(QString, retVal),
               Q_ARG(QString, "sqrt"),
               Q_ARG(int, 42),
               Q_ARG(double, 9.7));

QMetaObject::normalizedSignature() is used here to ensure that the format of the signature is what invoke() expects. E.g. extra whitespace is removed.

If the "compute" slot does not take exactly one QString, one int and one double in the specified order, the call will fail.

See also Q_ARG(), Q_RETURN_ARG(), qRegisterMetaType(), and QMetaObject::invokeMethod().

bool QMetaMethod::invoke ( QObject * object, QGenericReturnArgument returnValue, QGenericArgument val0 = QGenericArgument( 0 ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument() ) const

This function overloads invoke().

This overload always invokes this method using the connection type Qt::AutoConnection.

bool QMetaMethod::invoke ( QObject * object, Qt::ConnectionType connectionType, QGenericArgument val0 = QGenericArgument( 0 ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument() ) const

This function overloads invoke().

This overload can be used if the return value of the member is of no interest.

bool QMetaMethod::invoke ( QObject * object, QGenericArgument val0 = QGenericArgument( 0 ), QGenericArgument val1 = QGenericArgument(), QGenericArgument val2 = QGenericArgument(), QGenericArgument val3 = QGenericArgument(), QGenericArgument val4 = QGenericArgument(), QGenericArgument val5 = QGenericArgument(), QGenericArgument val6 = QGenericArgument(), QGenericArgument val7 = QGenericArgument(), QGenericArgument val8 = QGenericArgument(), QGenericArgument val9 = QGenericArgument() ) const

This function overloads invoke().

This overload invokes this method using the connection type Qt::AutoConnection and ignores return values.