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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

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

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 )

Constructs a signal object called name, with the parent object parent. These arguments are passed directly to QObject.

### QSignal::~QSignal ()

Destroys the signal. All connections are removed, as is the case with all QObjects.

### 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 )

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

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 )

Connects the signal to member in object receiver.

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

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

Disonnects the signal from member in object receiver.

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

### bool QSignal::isBlocked () const

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

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

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

### void QSignal::setParameter ( int value )

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

### void QSignal::setValue ( const QVariant & value )

Sets the signal's parameter to value

### QVariant QSignal::value () const

Returns the signal's parameter

This file is part of the Qt toolkit. Copyright © 1995-2002 Trolltech. All Rights Reserved.