Detailed Description
The QObject class is the base class of all Qt objects.
QObject is the heart of the Qt object model. The central feature in this model is a very powerful
mechanism for seamless object communication called signals and slots. You can
connect a signal to a slot with connect() and destroy the
connection with disconnect(). To avoid never ending notification
loops you can temporarily block signals with blockSignals(). The
protected functions connectNotify() and disconnectNotify() make it
possible to track connections.
QObjects organize themselves in object trees. When you create a
QObject with another object as parent, the object will
automatically do an insertChild() on the parent and thus show up
in the parent's children() list. The parent takes ownership of the
object i.e. it will automatically delete its children in its
destructor. You can look for an object by name and optionally type
using child() or queryList(), and get the list of tree roots using
objectTrees().
Every object has an object name() and can report its className()
and whether it inherits() another class in the QObject inheritance
hierarchy.
When an object is deleted, it emits a destroyed() signal. You can
catch this signal to avoid dangling references to QObjects. The
QGuardedPtr class provides an elegant way to use this feature.
QObjects can receive events through event() and filter the events
of other objects. See installEventFilter() and eventFilter() for
details. A convenience handler, childEvent(), can be reimplemented
to catch child events.
Last but not least, QObject provides the basic timer support in
Qt; see QTimer for high-level support for timers.
Notice that the Q_OBJECT macro is mandatory for any object that
implements signals, slots or properties. You also need to run the
moc program (Meta Object Compiler) on the
source file. We strongly recommend the use of this macro in all
subclasses of QObject regardless of whether or not they actually
use signals, slots and properties, since failure to do so may lead
certain functions to exhibit undefined behaviour.
All Qt widgets inherit QObject. The convenience function
isWidgetType() returns whether an object is actually a widget. It
is much faster than inherits( "QWidget" ).
Some QObject functions, e.g. children(), objectTrees() and
queryList() return a QObjectList. A QObjectList is a QPtrList of
QObjects. QObjectLists support the same operations as QPtrLists
and have an iterator class, QObjectListIt.
See also Object Model.
Member Function Documentation
QObject::QObject ( QObject * parent = 0, const char * name = 0 )
Constructs an object called name with parent object, parent.
The parent of an object may be viewed as the object's owner. For
instance, a dialog box is the parent of the
"OK" and "Cancel" buttons it contains.
The destructor of a parent object destroys all child objects.
Setting parent to 0 constructs an object with no parent. If the
object is a widget, it will become a top-level window.
The object name is some text that can be used to identify a
QObject. It's particularly useful in conjunction with Qt Designer. You can find an
object by name (and type) using child(). To find several objects
use queryList().
See also parent(), name, child(), and queryList().
QObject::~QObject () [virtual]
Destroys the object, deleting all its child objects.
All signals to and from the object are automatically disconnected.
Warning: All child objects are deleted. If any of these objects
are on the stack or global, sooner or later your program will
crash. We do not recommend holding pointers to child objects from
outside the parent. If you still do, the QObject::destroyed()
signal gives you an opportunity to detect when an object is
destroyed.
Warning: Deleting a QObject while pending events are waiting to be
delivered can cause a crash. You must not delete the QObject
directly from a thread that is not the GUI thread. Use the
QObject::deleteLater() method instead, which will cause the event
loop to delete the object after all pending events have been
delivered to the object.
void QObject::blockSignals ( bool block )
Blocks signals if block is TRUE, or unblocks signals if block is FALSE.
Emitted signals disappear into hyperspace if signals are blocked.
Note that the destroyed() signals will be emitted even if the signals
for this object have been blocked.
Examples: rot13/rot13.cpp and simple/main.cpp.
bool QObject::checkConnectArgs ( const char * signal, const QObject * receiver, const char * member ) [virtual protected]
Returns TRUE if the signal and the member arguments are
compatible; otherwise returns FALSE. (The receiver argument is
currently ignored.)
Warning: We recommend that you use the default implementation and
do not reimplement this function.
QObject * QObject::child ( const char * objName, const char * inheritsClass = 0, bool recursiveSearch = TRUE )
Searches the children and optionally grandchildren of this object,
and returns a child that is called objName that inherits inheritsClass. If inheritsClass is 0 (the default), any class
matches.
If recursiveSearch is TRUE (the default), child() performs a
depth-first search of the object's children.
If there is no such object, this function returns 0. If there are
more than one, the first one found is retured; if you need all of
them, use queryList().
void QObject::childEvent ( QChildEvent * ) [virtual protected]
This event handler can be reimplemented in a subclass to receive
child events.
Child events are sent to objects when children are inserted or
removed.
Note that events with QEvent::type() QEvent::ChildInserted are
posted (with QApplication::postEvent()) to make sure that the
child's construction is completed before this function is called.
If a child is removed immediately after it is inserted, the ChildInserted event may be suppressed, but the ChildRemoved
event will always be sent. In such cases it is possible that there
will be a ChildRemoved event without a corresponding ChildInserted event.
If you change state based on ChildInserted events, call
QWidget::constPolish(), or do
QApplication::sendPostedEvents( this, QEvent::ChildInserted );
in functions that depend on the state. One notable example is
QWidget::sizeHint().
See also event() and QChildEvent.
Reimplemented in QMainWindow and QSplitter.
const QObjectList * QObject::children () const
Returns a list of child objects, or 0 if this object has no
children.
The QObjectList class is defined in the qobjectlist.h header
file.
The first child added is the first
object in the list and the last child added is the last object in the list, i.e. new
children are appended at the end.
Note that the list order changes when QWidget children are raised or lowered. A widget that is raised becomes the last object
in the list, and a widget that is lowered becomes the first object
in the list.
See also child(), queryList(), parent(), insertChild(), and removeChild().
const char * QObject::className () const [virtual]
Returns the class name of this object.
This function is generated by the Meta
Object Compiler.
Warning: This function will return the wrong name if the class
definition lacks the Q_OBJECT macro.
See also name, inherits(), isA(), and isWidgetType().
Example: sql/overview/custom1/main.cpp.
bool QObject::connect ( const QObject * sender, const char * signal, const QObject * receiver, const char * member ) [static]
Connects signal from the sender object to member in object
receiver, and returns TRUE if the connection succeeds; otherwise
returns FALSE.
You must use the SIGNAL() and SLOT() macros when specifying the signal
and the member, for example:
QLabel *label = new QLabel;
QScrollBar *scroll = new QScrollBar;
QObject::connect( scroll, SIGNAL(valueChanged(int)),
label, SLOT(setNum(int)) );
This example ensures that the label always displays the current
scroll bar value. Note that the signal and slots parameters must not
contain any variable names, only the type. E.g. the following would
not work and return FALSE:
QObject::connect( scroll, SIGNAL(valueChanged(int v)),
label, SLOT(setNum(int v)) );
A signal can also be connected to another signal:
class MyWidget : public QWidget
{
Q_OBJECT
public:
MyWidget();
signals:
void myUsefulSignal();
private:
QPushButton *aButton;
};
MyWidget::MyWidget()
{
aButton = new QPushButton( this );
connect( aButton, SIGNAL(clicked()), SIGNAL(myUsefulSignal()) );
}
In this example, the MyWidget constructor relays a signal from a
private member variable, and makes it available under a name that
relates to MyWidget.
A signal can be connected to many slots and signals. Many signals
can be connected to one slot.
If a signal is connected to several slots, the slots are activated
in an arbitrary order when the signal is emitted.
The function returns TRUE if it successfully connects the signal
to the slot. It will return FALSE if it cannot create the
connection, for example, if QObject is unable to verify the
existence of either signal or member, or if their signatures
aren't compatible.
A signal is emitted for every connection you make, so if you
duplicate a connection, two signals will be emitted. You can
always break a connection using disconnect().
See also disconnect().
Examples: action/main.cpp, application/main.cpp, extension/main.cpp, iconview/main.cpp, network/archivesearch/main.cpp, regexptester/main.cpp, and t2/main.cpp.
bool QObject::connect ( const QObject * sender, const char * signal, const char * member ) const
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Connects signal from the sender object to this object's member.
Equivalent to: QObject::connect(sender, signal, this, member).
See also disconnect().
void QObject::connectNotify ( const char * signal ) [virtual protected]
This virtual function is called when something has been connected
to signal in this object.
Warning: This function violates the object-oriented principle of
modularity. However, it might be useful when you need to perform
expensive initialization only if something is connected to a
signal.
See also connect() and disconnectNotify().
void QObject::customEvent ( QCustomEvent * ) [virtual protected]
This event handler can be reimplemented in a subclass to receive
custom events. Custom events are user-defined events with a type
value at least as large as the "User" item of the QEvent::Type
enum, and is typically a QCustomEvent or QCustomEvent subclass.
See also event() and QCustomEvent.
void QObject::deleteLater () [slot]
Performs a deferred deletion of this object.
Instead of an immediate deletion this function schedules a
deferred delete event for processing when Qt returns to the main
event loop.
Example: table/bigtable/main.cpp.
void QObject::destroyed () [signal]
This signal is emitted when the object is being destroyed.
Note that the signal is emitted by the QObject destructor, so
the object's virtual table is already degenerated at this point,
and it is not safe to call any functions on the object emitting
the signal. This signal can not be blocked.
All the objects's children are destroyed immediately after this
signal is emitted.
void QObject::destroyed ( QObject * obj ) [signal]
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
This signal is emitted immediately before the object obj is
destroyed, and can not be blocked.
All the objects's children are destroyed immediately after this
signal is emitted.
bool QObject::disconnect ( const QObject * sender, const char * signal, const QObject * receiver, const char * member ) [static]
Disconnects signal in object sender from member in object
receiver.
A signal-slot connection is removed when either of the objects
involved are destroyed.
disconnect() is typically used in three ways, as the following
examples demonstrate.
- Disconnect everything connected to an object's signals:
disconnect( myObject, 0, 0, 0 );
equivalent to the non-static overloaded function
myObject->disconnect();
- Disconnect everything connected to a specific signal:
disconnect( myObject, SIGNAL(mySignal()), 0, 0 );
equivalent to the non-static overloaded function
myObject->disconnect( SIGNAL(mySignal()) );
- Disconnect a specific receiver:
disconnect( myObject, 0, myReceiver, 0 );
equivalent to the non-static overloaded function
myObject->disconnect( myReceiver );
0 may be used as a wildcard, meaning "any signal", "any receiving
object", or "any slot in the receiving object", respectively.
The sender may never be 0. (You cannot disconnect signals from
more than one object in a single call.)
If signal is 0, it disconnects receiver and member from
any signal. If not, only the specified signal is disconnected.
If receiver is 0, it disconnects anything connected to signal. If not, slots in objects other than receiver are not
disconnected.
If member is 0, it disconnects anything that is connected to receiver. If not, only slots named member will be disconnected,
and all other slots are left alone. The member must be 0 if receiver is left out, so you cannot disconnect a
specifically-named slot on all objects.
See also connect().
bool QObject::disconnect ( const char * signal = 0, const QObject * receiver = 0, const char * member = 0 )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Disconnects signal from member of receiver.
A signal-slot connection is removed when either of the objects
involved are destroyed.
bool QObject::disconnect ( const QObject * receiver, const char * member = 0 )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Disconnects all signals in this object from receiver's member.
A signal-slot connection is removed when either of the objects
involved are destroyed.
void QObject::disconnectNotify ( const char * signal ) [virtual protected]
This virtual function is called when something has been
disconnected from signal in this object.
Warning: This function violates the object-oriented principle of
modularity. However, it might be useful for optimizing access to
expensive resources.
See also disconnect() and connectNotify().
void QObject::dumpObjectInfo ()
Dumps information about signal connections, etc. for this object
to the debug output.
This function is useful for debugging, but does nothing if the
library has been compiled in release mode (i.e. without debugging
information).
void QObject::dumpObjectTree ()
Dumps a tree of children to the debug output.
This function is useful for debugging, but does nothing if the
library has been compiled in release mode (i.e. without debugging
information).
bool QObject::event ( QEvent * e ) [virtual]
This virtual function receives events to an object and should
return TRUE if the event e was recognized and processed.
The event() function can be reimplemented to customize the
behavior of an object.
See also installEventFilter(), timerEvent(), QApplication::sendEvent(), QApplication::postEvent(), and QWidget::event().
Reimplemented in QWidget.
bool QObject::eventFilter ( QObject * watched, QEvent * e ) [virtual]
Filters events if this object has been installed as an event
filter for the watched object.
In your reimplementation of this function, if you want to filter
the event e, out, i.e. stop it being handled further, return
TRUE; otherwise return FALSE.
Example:
class MyMainWindow : public QMainWindow
{
public:
MyMainWindow( QWidget *parent = 0, const char *name = 0 );
protected:
bool eventFilter( QObject *obj, QEvent *ev );
private:
QTextEdit *textEdit;
};
MyMainWindow::MyMainWindow( QWidget *parent, const char *name )
: QMainWindow( parent, name )
{
textEdit = new QTextEdit( this );
setCentralWidget( textEdit );
textEdit->installEventFilter( this );
}
bool MyMainWindow::eventFilter( QObject *obj, QEvent *ev )
{
if ( obj == textEdit ) {
if ( e->type() == QEvent::KeyPress ) {
QKeyEvent *k = (QKeyEvent*)ev;
qDebug( "Ate key press %d", k->key() );
return TRUE;
} else {
return FALSE;
}
} else {
// pass the event on to the parent class
return QMainWindow::eventFilter( obj, ev );
}
}
Notice in the example above that unhandled events are passed to
the base class's eventFilter() function, since the base class
might have reimplemented eventFilter() for its own internal
purposes.
Warning: If you delete the receiver object in this function, be
sure to return TRUE. Otherwise, Qt will forward the event to the
deleted object and the program might crash.
See also installEventFilter().
Reimplemented in QAccel, QScrollView, and QSpinBox.
bool QObject::highPriority () const
Returns TRUE if the object is a high-priority object, or FALSE if
it is a standard-priority object.
High-priority objects are placed first in QObject's list of
children on the assumption that they will be referenced very
often.
bool QObject::inherits ( const char * clname ) const
Returns TRUE if this object is an instance of a class that
inherits clname, and clname inherits QObject; otherwise
returns FALSE.
A class is considered to inherit itself.
Example:
QTimer *t = new QTimer; // QTimer inherits QObject
t->inherits( "QTimer" ); // returns TRUE
t->inherits( "QObject" ); // returns TRUE
t->inherits( "QButton" ); // returns FALSE
// QScrollBar inherits QWidget and QRangeControl
QScrollBar *s = new QScrollBar( 0 );
s->inherits( "QWidget" ); // returns TRUE
s->inherits( "QRangeControl" ); // returns FALSE
(QRangeControl is not a QObject.)
See also isA() and metaObject().
Examples: table/statistics/statistics.cpp, themes/metal.cpp, and themes/wood.cpp.
void QObject::insertChild ( QObject * obj ) [virtual]
Inserts an object obj into the list of child objects.
Warning: This function cannot be used to make one widget the child
widget of another widget. Child widgets can only be created by
setting the parent widget in the constructor or by calling
QWidget::reparent().
See also removeChild() and QWidget::reparent().
void QObject::installEventFilter ( const QObject * filterObj )
Installs an event filter filterObj on this object. For example:
monitoredObj->installEventFilter( filterObj );
An event filter is an object that receives all events that are
sent to this object. The filter can either stop the event or
forward it to this object. The event filter filterObj receives
events via its eventFilter() function. The eventFilter() function
must return TRUE if the event should be filtered, (i.e. stopped);
otherwise it must return FALSE.
If multiple event filters are installed on a single object, the
filter that was installed last is activated first.
Here's a KeyPressEater class that eats the key presses of its
monitored objects:
class KeyPressEater : public QObject
{
...
protected:
bool eventFilter( QObject *o, QEvent *e );
};
bool KeyPressEater::eventFilter( QObject *o, QEvent *e )
{
if ( e->type() == QEvent::KeyPress ) {
// special processing for key press
QKeyEvent *k = (QKeyEvent *)e;
qDebug( "Ate key press %d", k->key() );
return TRUE; // eat event
} else {
// standard event processing
return FALSE;
}
}
And here's how to install it on two widgets:
KeyPressEater *keyPressEater = new KeyPressEater( this );
QPushButton *pushButton = new QPushButton( this );
QListView *listView = new QListView( this );
pushButton->installEventFilter( keyPressEater );
listView->installEventFilter( keyPressEater );
The QAccel class, for example, uses this technique to intercept
accelerator key presses.
Warning: If you delete the receiver object in your eventFilter()
function, be sure to return TRUE. If you return FALSE, Qt sends
the event to the deleted object and the program will crash.
See also removeEventFilter(), eventFilter(), and event().
bool QObject::isA ( const char * clname ) const
Returns TRUE if this object is an instance of the class clname;
otherwise returns FALSE.
Example:
QTimer *t = new QTimer; // QTimer inherits QObject
t->isA( "QTimer" ); // returns TRUE
t->isA( "QObject" ); // returns FALSE
See also inherits() and metaObject().
bool QObject::isWidgetType () const
Returns TRUE if the object is a widget; otherwise returns FALSE.
Calling this function is equivalent to calling
inherits("QWidget"), except that it is much faster.
void QObject::killTimer ( int id )
Kills the timer with timer identifier, id.
The timer identifier is returned by startTimer() when a timer
event is started.
See also timerEvent(), startTimer(), and killTimers().
void QObject::killTimers ()
Kills all timers that this object has started.
Warning: Using this function can cause hard-to-find bugs: it kills
timers started by sub- and superclasses as well as those started
by you, which is often not what you want. We recommend using a
QTimer or perhaps killTimer().
See also timerEvent(), startTimer(), and killTimer().
QMetaObject * QObject::metaObject () const [virtual]
Returns a pointer to the meta object of this object.
A meta object contains information about a class that inherits
QObject, e.g. class name, superclass name, properties, signals and
slots. Every class that contains the Q_OBJECT macro will also have
a meta object.
The meta object information is required by the signal/slot
connection mechanism and the property system. The functions isA()
and inherits() also make use of the meta object.
const char * QObject::name () const
Returns the name of this object.
See the "name" property for details.
const char * QObject::name ( const char * defaultName ) const
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns the name of this object, or defaultName if the object
does not have a name.
QCString QObject::normalizeSignalSlot ( const char * signalSlot ) [static protected]
Normlizes the signal or slot definition signalSlot by removing
unnecessary whitespace.
const QObjectList * QObject::objectTrees () [static]
Returns a pointer to the list of all object trees (their root
objects), or 0 if there are no objects.
The QObjectList class is defined in the qobjectlist.h header
file.
The most recent root object created is the first object in the list and the first root object added
is the last object in the list.
See also children(), parent(), insertChild(), and removeChild().
QObject * QObject::parent () const
Returns a pointer to the parent object.
See also children().
QVariant QObject::property ( const char * name ) const [virtual]
Returns the value of the object's name property.
If no such property exists, the returned variant is invalid.
Information about all available properties are provided through
the metaObject().
See also setProperty(), QVariant::isValid(), metaObject(), QMetaObject::propertyNames(), and QMetaObject::property().
Example: qutlook/centralwidget.cpp.
QObjectList * QObject::queryList ( const char * inheritsClass = 0, const char * objName = 0, bool regexpMatch = TRUE, bool recursiveSearch = TRUE ) const
Searches the children and optionally grandchildren of this object,
and returns a list of those objects that are named or that match
objName and inherit inheritsClass. If inheritsClass is 0
(the default), all classes match. If objName is 0 (the
default), all object names match.
If regexpMatch is TRUE (the default), objName is a regular expression that the objects's names must match. The syntax is that
of a QRegExp. If regexpMatch is FALSE, objName is a string
and object names must match it exactly.
Note that inheritsClass uses single inheritance from QObject,
the way inherits() does. According to inherits(), QMenuBar
inherits QWidget but not QMenuData. This does not quite match
reality, but is the best that can be done on the wide variety of
compilers Qt supports.
Finally, if recursiveSearch is TRUE (the default), queryList()
searches nth-generation as well as first-generation children.
If all this seems a bit complex for your needs, the simpler
child() function may be what you want.
This somewhat contrived example disables all the buttons in this
window:
QObjectList *l = topLevelWidget()->queryList( "QButton" );
QObjectListIt it( *l ); // iterate over the buttons
QObject *obj;
while ( (obj = it.current()) != 0 ) {
// for each found object...
++it;
((QButton*)obj)->setEnabled( FALSE );
}
delete l; // delete the list, not the objects
The QObjectList class is defined in the qobjectlist.h header
file.
Warning: Delete the list as soon you have finished using it. The
list contains pointers that may become invalid at almost any time
without notice (as soon as the user closes a window you may have
dangling pointers, for example).
See also child(), children(), parent(), inherits(), name, and QRegExp.
void QObject::removeChild ( QObject * obj ) [virtual]
Removes the child object obj from the list of children.
Warning: This function will not remove a child widget from the
screen. It will only remove it from the parent widget's list of
children.
See also insertChild() and QWidget::reparent().
void QObject::removeEventFilter ( const QObject * obj )
Removes an event filter object obj from this object. The
request is ignored if such an event filter has not been installed.
All event filters for this object are automatically removed when
this object is destroyed.
It is always safe to remove an event filter, even during event
filter activation (i.e. from the eventFilter() function).
See also installEventFilter(), eventFilter(), and event().
const QObject * QObject::sender () [protected]
Returns a pointer to the object that sent the signal, if called in
a slot activated by a signal; otherwise it returns 0. The pointer
is valid only during the execution of the slot that calls this
function.
The pointer returned by this function becomes invalid if the
sender is destroyed, or if the slot is disconnected from the
sender's signal.
Warning: This function violates the object-oriented principle of
modularity. However, getting access to the sender might be useful
when many signals are connected to a single slot. The sender is
undefined if the slot is called as a normal C++ function.
void QObject::setName ( const char * name ) [virtual]
Sets the object's name to name.
bool QObject::setProperty ( const char * name, const QVariant & value ) [virtual]
Sets the value of the object's name property to value.
Returns TRUE if the operation was successful; otherwise returns
FALSE.
Information about all available properties is provided through the
metaObject().
See also property(), metaObject(), QMetaObject::propertyNames(), and QMetaObject::property().
Example: qutlook/centralwidget.cpp.
bool QObject::signalsBlocked () const
Returns TRUE if signals are blocked; otherwise returns FALSE.
Signals are not blocked by default.
See also blockSignals().
int QObject::startTimer ( int interval )
Starts a timer and returns a timer identifier, or returns zero if
it could not start a timer.
A timer event will occur every interval milliseconds until
killTimer() or killTimers() is called. If interval is 0, then
the timer event occurs once every time there are no more window
system events to process.
The virtual timerEvent() function is called with the QTimerEvent
event parameter class when a timer event occurs. Reimplement this
function to get timer events.
If multiple timers are running, the QTimerEvent::timerId() can be
used to find out which timer was activated.
Example:
class MyObject : public QObject
{
Q_OBJECT
public:
MyObject( QObject *parent = 0, const char *name = 0 );
protected:
void timerEvent( QTimerEvent * );
};
MyObject::MyObject( QObject *parent, const char *name )
: QObject( parent, name )
{
startTimer( 50 ); // 50-millisecond timer
startTimer( 1000 ); // 1-second timer
startTimer( 60000 ); // 1-minute timer
}
void MyObject::timerEvent( QTimerEvent *e )
{
qDebug( "timer event, id %d", e->timerId() );
}
Note that QTimer's accuracy depends on the underlying operating
system and hardware. Most platforms support an accuracy of 20 ms;
some provide more. If Qt is unable to deliver the requested
number of timer clicks, it will silently discard some.
The QTimer class provides a high-level programming interface with
one-shot timers and timer signals instead of events.
See also timerEvent(), killTimer(), killTimers(), QEventLoop::awake(), and QEventLoop::aboutToBlock().
void QObject::timerEvent ( QTimerEvent * ) [virtual protected]
This event handler can be reimplemented in a subclass to receive
timer events for the object.
QTimer provides a higher-level interface to the timer
functionality, and also more general information about timers.
See also startTimer(), killTimer(), killTimers(), and event().
Examples: biff/biff.cpp, dclock/dclock.cpp, forever/forever.cpp, grapher/grapher.cpp, qmag/qmag.cpp, and xform/xform.cpp.
QString QObject::tr ( const char * sourceText, const char * comment ) [static]
Returns a translated version of sourceText, or sourceText
itself if there is no appropriate translated version. The
translation context is QObject with comment (0 by default).
All QObject subclasses using the Q_OBJECT macro automatically have
a reimplementation of this function with the subclass name as
context.
Warning: This method is reentrant only if all translators are
installed before calling this method. Installing or removing
translators while performing translations is not supported. Doing
so will probably result in crashes or other undesirable behavior.
See also trUtf8(), QApplication::translate(), and Internationalization with Qt.
Example: network/networkprotocol/view.cpp.
QString QObject::trUtf8 ( const char * sourceText, const char * comment ) [static]
Returns a translated version of sourceText, or
QString::fromUtf8(sourceText) if there is no appropriate
version. It is otherwise identical to tr(sourceText, comment).
Warning: This method is reentrant only if all translators are
installed before calling this method. Installing or removing
translators while performing translations is not supported. Doing
so will probably result in crashes or other undesirable behavior.
See also tr() and QApplication::translate().
Property Documentation
This property holds the name of this object.
You can find an object by name (and type) using child(). You can
find a set of objects with queryList().
The object name is set by the constructor or by the setName()
function. The object name is not very useful in the current
version of Qt, but will become increasingly important in the
future.
If the object does not have a name, the name() function returns
"unnamed", so printf() (used in qDebug()) will not be asked to
output a null pointer. If you want a null pointer to be returned
for unnamed objects, you can call name( 0 ).
qDebug( "MyClass::setPrecision(): (%s) invalid precision %f",
name(), newPrecision );
See also className(), child(), and queryList().
Set this property's value with setName() and get this property's value with name().
Related Functions
void * qt_find_obj_child ( QObject * parent, const char * type, const char * name )
Returns a pointer to the object named name that inherits type and with a given parent.
Returns 0 if there is no such child.
QListBox *c = (QListBox *) qt_find_obj_child( myWidget, "QListBox",
"my list box" );
if ( c )
c->insertItem( "another string" );
This file is part of the Qt toolkit.
Copyright © 1995-2005
Trolltech. All Rights Reserved.
