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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="NSAutoreleasePool" up="Base">
<head>
<title>NSAutoreleasePool 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>
<copy>1995, 1996, 1997 Free Software Foundation, Inc.</copy>
</head>
<body>
<front><contents /></front>
<chapter>
<heading>
Software documentation for the NSAutoreleasePool class
</heading>
<class name="NSAutoreleasePool" super="NSObject" ovadd="1.0.0">
<declared>Foundation/NSAutoreleasePool.h</declared>
<desc>
<p>
The standard OpenStep system of memory management
employs retain counts. When an object is created,
it has a retain count of 1. When an object is retained,
the retain count is incremented. When it is released
the retain count is decremented, and when the retain
count goes to zero the object gets deallocated.
</p>
<p>
A simple retain/release mechanism has problems with
passing objects from one scope to another, so it's
augmented with autorelease pools. You can use the
<ref type="function" id="AUTORELEASE">
AUTORELEASE()
</ref>
macro to call the
<ref type="method" id="-autorelease" class="NSObject">
[NSObject -autorelease]
</ref>
method, which adds an object to the current
autorelease pool by calling
<ref type="method" id="+addObject:" class="NSAutoreleasePool">[NSAutoreleasePool +addObject:]</ref>. <br /> An autorelease pool simply maintains a reference to each object added to it, and for each addition, the autorelease pool will call the <ref type="method" id="-release" class="NSObject">[NSObject -release]</ref> method of the object when the pool is released. So doing an <ref type="function" id="AUTORELEASE">AUTORELEASE()</ref> is just the same as doing a <ref type="function" id="RELEASE">RELEASE()</ref>, but deferred until the current autorelease pool is deallocated.
</p>
<p>
The NSAutoreleasePool class maintains a separate stack
of autorelease pools objects in each thread.
</p>
<p>
When an autorelease pool is created, it is
automatically added to the stack of pools in
the thread.
</p>
<p>
When a pool is destroyed, it (and any pool later in
the stack) is removed from the stack.
</p>
<p>
This mechanism provides a simple but controllable and
reasonably efficient way of managing temporary
objects. An object can be autoreleased and then
passed around and used until the topmost pool in the
stack is destroyed.
</p>
<p>
Most methods return objects which are either owned by
autorelease pools or by the receiver of the
method, so the lifetime of the returned object can
be assumed to be the shorter of the lifetime of the
current autorelease pool, or that of the receiver
on which the method was called. <br /> The exceptions to
this are those object returned by -
</p>
<deflist>
<term>
<ref type="method" id="+alloc" class="NSObject">
[NSObject +alloc]
</ref>
,
<ref type="method" id="+allocWithZone:" class="NSObject">[NSObject +allocWithZone:]</ref>
</term>
<desc>
Methods whose names begin with alloc return an
uninitialised object, owned by the caller.
</desc>
<term>
<ref type="method" id="-init" class="NSObject">
[NSObject -init]
</ref>
</term>
<desc>
Methods whose names begin with init return an
initialised version of the receiving object,
owned by the caller. <br /> NB. The returned object
may not actually be the same as the receiver...
sometimes an init method releases the original
receiver and returns an alternative.
</desc>
<term>
<ref type="method" id="+new" class="NSObject">
[NSObject +new]
</ref>
</term>
<desc>
Methods whose names begin with new combine the
effects of allocation and initialisation.
</desc>
<term>
<ref type="method" id="-copy" class="NSObject">
[NSObject -copy]
</ref>
,
<ref type="method" id="-copyWithZone:" class="(NSCopying)">[<NSCopying>-copyWithZone:]</ref>
</term>
<desc>
Methods whose names begin with copy create a copy
of the receiver which is owned by the caller.
</desc>
<term>
<ref type="method" id="-mutableCopy" class="NSObject">
[NSObject -mutableCopy]
</ref>
,
<ref type="method" id="-mutableCopyWithZone:" class="(NSMutableCopying)">[<NSMutableCopying>-mutableCopyWithZone:]</ref>
</term>
<desc>
Methods whose names begin with mutableCopy create
a copy of the receiver which is owned by the caller.
</desc>
</deflist>
</desc>
<ivariable type="void(*" name="_addImp" validity="protected" ovadd="1.0.0">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSAutoreleasePool*" name="_child" validity="protected" ovadd="1.0.0">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSAutoreleasePool*" name="_parent" validity="protected" ovadd="1.0.0">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="struct autorelease_array_list*" name="_released" validity="protected" ovadd="1.0.0">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="unsigned int" name="_released_count" validity="protected" ovadd="1.0.0">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="struct autorelease_array_list*" name="_released_head" validity="protected" ovadd="1.0.0">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<method type="void" factory="yes" ovadd="1.0.0">
<sel>addObject:</sel>
<arg type="id">anObj</arg>
<desc>
Adds <var>anObj</var> to the current autorelease pool.
<br /> If there is no autorelease pool in the
thread, a warning is logged and the object is
leaked (ie it will not be released).
</desc>
</method>
<method type="id" factory="yes" ovadd="1.0.0">
<sel>allocWithZone:</sel>
<arg type="NSZone*">zone</arg>
<desc>
Allocate and return an autorelease pool instance.
<br /> If there is an already-allocated
NSAutoreleasePool available, save time by
just returning that, rather than allocating a new one.
<br /> The pool instance becomes the current
autorelease pool for this thread.
</desc>
</method>
<method type="unsigned" factory="yes" ovadd="0.0.0" ovrem="0.0.0">
<sel>autoreleaseCountForObject:</sel>
<arg type="id">anObject</arg>
<desc>
<p>
Counts the number of times that the specified
object occurs in autorelease pools in the current
thread.
</p>
<p>
This method is <em>slow</em> and should probably
only be used for debugging purposes.
</p>
</desc>
</method>
<method type="id" factory="yes" ovadd="0.0.0" ovrem="0.0.0">
<sel>currentPool</sel>
<desc>
Return the currently active autorelease pool.
</desc>
</method>
<method type="void" factory="yes" ovadd="0.0.0" ovrem="0.0.0">
<sel>enableRelease:</sel>
<arg type="BOOL">enable</arg>
<desc>
<p>
Specifies whether objects contained in
autorelease pools are to be released when the
pools are deallocated (by default <code>YES</code>
).
</p>
<p>
You can set this to <code>NO</code> for debugging
purposes.
</p>
</desc>
</method>
<method type="void" factory="yes" ovadd="0.0.0" ovrem="0.0.0">
<sel>freeCache</sel>
<desc>
<p>
When autorelease pools are deallocated, the memory
they used is retained in a cache for re-use so that
new polls can be created very quickly.
</p>
<p>
This method may be used to empty that cache,
ensuring that the minimum memory is used by the
application.
</p>
</desc>
</method>
<method type="void" factory="yes" ovadd="0.0.0" ovrem="0.0.0">
<sel>setPoolCountThreshold:</sel>
<arg type="unsigned">c</arg>
<desc>
<p>
Specifies a limit to the number of objects that
may be added to an autorelease pool. When this limit
is reached an exception is raised.
</p>
<p>
You can set this to a smallish value to catch
problems with code that autoreleases too many
objects to operate efficiently.
</p>
<p>
Default value is maxint.
</p>
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>addObject:</sel>
<arg type="id">anObj</arg>
<desc>
Adds <var>anObj</var> to this autorelease pool.
</desc>
</method>
<method type="id" ovadd="1.0.0">
<sel>autorelease</sel>
<desc>
Raises an exception - pools should not be
autoreleased.
</desc>
</method>
<method type="unsigned" ovadd="0.0.0" ovrem="0.0.0">
<sel>autoreleaseCount</sel>
<desc>
Return the number of objects in this pool.
</desc>
</method>
<method type="void" ovadd="10.4.0">
<sel>drain</sel>
<desc>
Intended to trigger a garbage collection run (if
needed) when called in a garbage collected
environment. <br /> In a non-garbage collected
environment, this method implements the
undocumented MacOS-X behavior, and releases
the receiver.
</desc>
</method>
<method type="void" ovadd="0.0.0" ovrem="0.0.0">
<sel>emptyPool</sel>
<desc>
Empties the current pool by releasing all the
autoreleased objects in it. Also destroys any
child pools (ones created after the receiver in the
same thread) causing any objects in those pools to be
released. <br /> This is a low cost (efficient)
method which may be used to get rid of autoreleased
objects in the pool, but carry on using the pool.
</desc>
</method>
<method type="oneway void" ovadd="1.0.0">
<sel>release</sel>
<desc>
Destroys the receiver (calls -dealloc).
</desc>
</method>
<method type="id" ovadd="1.0.0">
<sel>retain</sel>
<desc>
Raises an exception... pools should not be retained.
</desc>
</method>
</class>
</chapter>
</body>
</gsdoc>
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