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<?xml version="1.0"?>
<!DOCTYPE gsdoc PUBLIC "-//GNUstep//DTD gsdoc 1.0.4//EN" "http://www.gnustep.org/gsdoc-1_0_4.dtd">
<gsdoc base="NSNotification" up="Base">
<head>
<title>NSNotificationCenter class reference</title>
<author name="Andrew Kachites McCallum">
<email address="mccallum@gnu.ai.mit.edu">
mccallum@gnu.ai.mit.edu
</email>
</author>
<author name="Richard Frith-Macdonald">
<email address="rfm@gnu.org">
rfm@gnu.org
</email>
</author>
<author name="Richard Frith-Macdonald">
<email address="richard@brainstorm.co.uk">
richard@brainstorm.co.uk
</email>
</author>
<copy>1996,1999 Free Software Foundation, Inc.</copy>
</head>
<body>
<front><contents /></front>
<chapter>
<heading>
Software documentation for the NSNotification class
</heading>
<class name="NSNotification" super="NSObject" ovadd="1.0.0">
<declared>Foundation/NSNotification.h</declared>
<conform>NSCopying</conform>
<conform>NSCoding</conform>
<desc>
<p>
Represents a notification for posting to an
<ref type="class" id="NSNotificationCenter">NSNotificationCenter</ref>. Consists of a name, an object, and an optional dictionary. The notification center will check for observers registered to receive either notifications with the name, the object, or both and pass the notification instance on to them.</p>
<p>
This class is actually the interface for a class
cluster, so instances will be of a (private)
subclass.
</p>
</desc>
<method type="NSNotification*" factory="yes" ovadd="1.0.0">
<sel>notificationWithName:</sel>
<arg type="NSString*">name</arg>
<sel>object:</sel>
<arg type="id">object</arg>
<desc>
Create a new autoreleased notification by calling
<ref type="method" id="+notificationWithName:object:userInfo:">+notificationWithName:object:userInfo:</ref> with a <code>nil</code> user info argument.
</desc>
</method>
<method type="NSNotification*" factory="yes" ovadd="1.0.0">
<sel>notificationWithName:</sel>
<arg type="NSString*">name</arg>
<sel>object:</sel>
<arg type="id">object</arg>
<sel>userInfo:</sel>
<arg type="NSDictionary*">info</arg>
<desc>
Create a new autoreleased notification.
</desc>
</method>
<method type="NSString*" ovadd="1.0.0">
<sel>name</sel>
<desc>
Returns the notification name.
</desc>
</method>
<method type="id" ovadd="1.0.0">
<sel>object</sel>
<desc>
Returns the notification object.
</desc>
</method>
<method type="NSDictionary*" ovadd="1.0.0">
<sel>userInfo</sel>
<desc>
Returns the notification user information.
</desc>
</method>
</class>
</chapter>
<chapter>
<heading>
Software documentation for the NSNotificationCenter
class
</heading>
<class name="NSNotificationCenter" super="NSObject" ovadd="1.0.0">
<declared>Foundation/NSNotification.h</declared>
<desc>
<p>
GNUstep provides a framework for sending messages
between objects within a process called
<em>notifications</em>. Objects register with an
<code>NSNotificationCenter</code> to be informed
whenever other objects post
<ref type="class" id="NSNotification">NSNotification</ref>
s to it matching certain criteria. The notification
center processes notifications synchronously --
that is, control is only returned to the
notification poster once every recipient of
the notification has received it and processed it.
Asynchronous processing is possible using an
<ref type="class" id="NSNotificationQueue">NSNotificationQueue</ref>.</p>
<p>
Obtain an instance using the
<ref type="method" id="+defaultCenter">
+defaultCenter
</ref>
method.
</p>
<p>
In a multithreaded process, notifications are always
sent on the thread that they are posted from.
</p>
<p>
Use the
<ref type="class" id="NSDistributedNotificationCenter">NSDistributedNotificationCenter</ref>for interprocess communications on the same machine.</p>
</desc>
<method type="NSNotificationCenter*" factory="yes" ovadd="1.0.0">
<sel>defaultCenter</sel>
<desc>
Returns the default notification center being used
for this task (process). This is used for all
notifications posted by the Base library
unless otherwise noted.
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>addObserver:</sel>
<arg type="id">observer</arg>
<sel>selector:</sel>
<arg type="SEL">selector</arg>
<sel>name:</sel>
<arg type="NSString*">name</arg>
<sel>object:</sel>
<arg type="id">object</arg>
<desc>
<p>
Registers <var>observer</var> to receive
notifications with the <var>name</var>
notificationName and/or containing
<var>object</var> (one or both of these two must be
non-nil; <code>nil</code> acts like a wildcard).
When a notification of <var>name</var>
<var>name</var> containing <var>object</var> is
posted, <var>observer</var> receives a
<var>selector</var> message with this notification
as the argument. The notification center waits for the
<var>observer</var> to finish processing the
message, then informs the next registree
matching the notification, and after all of this
is done, control returns to the poster of the
notification. Therefore the processing in
the <var>selector</var> implementation should be
<strong>short</strong>.
</p>
<p>
The notification center does not retain
<var>observer</var> or <var>object</var>.
Therefore, you should always send
removeObserver: or
removeObserver:name:object:
to the notification center before releasing these
objects. <br /> As a convenience, when built
with garbage collection, you do not need to remove
any garbage collected <var>observer</var> as the
system will do it implicitly.
</p>
<p>
NB. For MacOS-X compatibility, adding an
<var>observer</var> multiple times will register it
to receive multiple copies of any matching
notification, however removing an
<var>observer</var> will remove <em>all</em> of the
multiple registrations.
</p>
</desc>
</method>
<method type="id" ovadd="10.6.0">
<sel>addObserverForName:</sel>
<arg type="NSString*">name</arg>
<sel>object:</sel>
<arg type="id">object</arg>
<sel>queue:</sel>
<arg type="NSOperationQueue*">queue</arg>
<sel>usingBlock:</sel>
<arg type="GSNotificationBlock">block</arg>
<desc>
<p>
Returns a new observer added to the notification
center, in order to observe the given
notification <var>name</var> posted by an
<var>object</var> or any <var>object</var> (if the
<var>object</var> argument is <code>nil</code>).
</p>
<p>
For the <var>name</var> and <var>object</var>
arguments, the constraints and behavior
described in
<ref type="method" id="-addObserver:name:selector:object:">-addObserver:name:selector:object:</ref> remain valid.
</p>
<p>
For each notification received by the center, the
observer will execute the notification
<var>block</var>. If the <var>queue</var> is not
<code>nil</code>, the notification
<var>block</var> is wrapped in a NSOperation and
scheduled in the <var>queue</var>, otherwise
the <var>block</var> is executed immediately in the
posting thread.
</p>
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>postNotification:</sel>
<arg type="NSNotification*">notification</arg>
<desc>
Posts <var>notification</var> to all the observers
that match its NAME and OBJECT. <br /> The GNUstep
implementation calls
<ref type="method" id="-postNotificationName:object:userInfo:">-postNotificationName:object:userInfo:</ref> to perform the actual posting.
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>postNotificationName:</sel>
<arg type="NSString*">name</arg>
<sel>object:</sel>
<arg type="id">object</arg>
<desc>
Creates and posts a notification using the
<ref type="method" id="-postNotificationName:object:userInfo:">-postNotificationName:object:userInfo:</ref> passing a <code>nil</code> user info argument.
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>postNotificationName:</sel>
<arg type="NSString*">name</arg>
<sel>object:</sel>
<arg type="id">object</arg>
<sel>userInfo:</sel>
<arg type="NSDictionary*">info</arg>
<desc>
The preferred method for posting a notification. <br />
For performance reasons, we don't wrap an exception
handler round every message sent to an observer.
This means that, if one observer raises an exception,
later observers in the lists will not get the
notification.
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>removeObserver:</sel>
<arg type="id">observer</arg>
<desc>
Deregisters <var>observer</var> from all
notifications. This should be called before
the <var>observer</var> is deallocated.
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>removeObserver:</sel>
<arg type="id">observer</arg>
<sel>name:</sel>
<arg type="NSString*">name</arg>
<sel>object:</sel>
<arg type="id">object</arg>
<desc>
Deregisters <var>observer</var> for
notifications matching <var>name</var> and/or
<var>object</var>. If either or both is
<code>nil</code>, they act like wildcards. The
<var>observer</var> may still remain registered for
other notifications; use
<ref type="method" id="-removeObserver:">
-removeObserver:
</ref>
to remove it from all. If <var>observer</var> is
<code>nil</code>, the effect is to remove all
registrees for the specified notifications,
unless both <var>observer</var> and <var>name</var>
are <code>nil</code>, in which case nothing is done.
</desc>
</method>
</class>
</chapter>
</body>
</gsdoc>
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