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QSignal Class Reference

The QSignal class can be used to send signals for classes that don't inherit QObject. More...

#include <qsignal.h>

Inherits QObject.

List of all member functions.

Public Members

• QSignal ( QObject * parent = 0, const char * name = 0 )
• ~QSignal ()
• bool connect ( const QObject * receiver, const char * member )
• bool disconnect ( const QObject * receiver, const char * member = 0 )
• void activate ()
• bool isBlocked () const  (obsolete)
• void block ( bool b )  (obsolete)
• void setParameter ( int value )  (obsolete)
• int parameter () const  (obsolete)
• void setValue ( const QVariant & value )
• QVariant value () const

Detailed Description

If you want to send signals from a class that does not inherit QObject, you can create an internal QSignal object to emit the signal. You must also provide a function that connects the signal to an outside object slot. This is how we have implemented signals in the QMenuData class, which is not a QObject.

In general, we recommend inheriting QObject instead. QObject provides much more functionality.

You can set a single QVariant parameter for the signal with setValue().

Note that QObject is a private base class of QSignal, i.e. you cannot call any QObject member functions from a QSignal object.

Example:

        #include <qsignal.h>

        class MyClass
        {
        public:
            MyClass();
            ~MyClass();

            void doSomething();

            void connect( QObject *receiver, const char *member );

        private:
            QSignal *sig;
        };

        MyClass::MyClass()
        {
            sig = new QSignal;
        }

        MyClass::~MyClass()
        {
            delete sig;
        }

        void MyClass::doSomething()
        {
            // ... does something
            sig->activate(); // emits the signal
        }

        void MyClass::connect( QObject *receiver, const char *member )
        {
            sig->connect( receiver, member );
        }
    

See also Input/Output and Networking and Miscellaneous Classes.

Member Function Documentation

QSignal::QSignal ( QObject * parent = 0, const char * name = 0 )

QSignal::~QSignal ()

void QSignal::activate ()

Emits the signal. If the platform supports QVariant and a parameter has been set with setValue(), this value is passed in the signal.

void QSignal::block ( bool b )

Blocks the signal if b is TRUE, or unblocks the signal if b is FALSE.

An activated signal disappears into hyperspace if it is blocked.

See also isBlocked(), activate(), and QObject::blockSignals().

bool QSignal::connect ( const QObject * receiver, const char * member )

See also disconnect() and QObject::connect().

bool QSignal::disconnect ( const QObject * receiver, const char * member = 0 )

See also connect() and QObject::disconnect().

bool QSignal::isBlocked () const

Returns TRUE if the signal is blocked, or FALSE if it is not blocked.

The signal is not blocked by default.

See also block() and QObject::signalsBlocked().

int QSignal::parameter () const

void QSignal::setParameter ( int value )

void QSignal::setValue ( const QVariant & value )

QVariant QSignal::value () const

This file is part of the Qt toolkit. Copyright © 1995-2003 Trolltech. All Rights Reserved.