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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="NSException" up="Base">
<head>
<title>NSAssertionHandler class reference</title>
<author name="Adam Fedor">
<email address="fedor@boulder.colorado.edu">
fedor@boulder.colorado.edu
</email>
</author>
<copy>1995, 1996 Free Software Foundation, Inc.</copy>
</head>
<body>
<front><contents /></front>
<chapter>
<heading>
Software documentation for the NSAssertionHandler
class
</heading>
<class name="NSAssertionHandler" super="NSObject" ovadd="1.0.0">
<declared>Foundation/NSException.h</declared>
<desc>
<p>
NSAssertionHandler objects are used to
raise exceptions on behalf of macros implementing
assertions. <br /> Each thread has its own
assertion handler instance. <br />
</p>
<p>
The macros work together with the assertion handler
object to produce meaningful exception messages
containing the name of the source file, the
position within that file, and the name of the
ObjC method or C function in which the assertion
failed.
</p>
<p>
An NSAssertionHandler instance is created on demand for
each thread and is stored in the thread's dictionary
under the key NSAssertionHandler. A custom
NSAssertionHandler can be used by adding
it to the thread dictionary under this key.
</p>
The assertion macros are:
<ref type="function" id="NSAssert">
NSAssert()
</ref>
, <ref type="function" id="NSCAssert">NSCAssert()</ref>,
<ref type="function" id="NSAssert1">
NSAssert1()
</ref>
, <ref type="function" id="NSCAssert1">NSCAssert1()</ref>,
<ref type="function" id="NSAssert2">
NSAssert2()
</ref>
, <ref type="function" id="NSCAssert2">NSCAssert2()</ref>,
<ref type="function" id="NSAssert3">
NSAssert3()
</ref>
, <ref type="function" id="NSCAssert3">NSCAssert3()</ref>,
<ref type="function" id="NSAssert4">
NSAssert4()
</ref>
, <ref type="function" id="NSCAssert4">NSCAssert4()</ref>,
<ref type="function" id="NSAssert5">
NSAssert5()
</ref>
, <ref type="function" id="NSCAssert5">NSCAssert5()</ref>,
<ref type="function" id="NSParameterAssert">
NSParameterAssert()
</ref>
,
<ref type="function" id="NSCParameterAssert">
NSCParameterAssert()
</ref>
<br /> The numbered macros arre obsolete, dating from
a time when
<ref type="function" id="NSAssert">
NSAssert()
</ref>
and <ref type="function" id="NSCAssert">NSCAssert()</ref>
did not support a variable number of arguments.
</desc>
<method type="NSAssertionHandler*" factory="yes" ovadd="1.0.0">
<sel>currentHandler</sel>
<desc>
Returns the assertion handler object for the
current thread. <br /> If none exists, creates one
and returns it.
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>handleFailureInFunction:</sel>
<arg type="NSString*">functionName</arg>
<sel>file:</sel>
<arg type="NSString*">fileName</arg>
<sel>lineNumber:</sel>
<arg type="NSInteger">line</arg>
<sel>description:</sel>
<arg type="NSString*">format</arg>
<vararg />
<desc>
Handles an assertion failure by using
<ref type="function" id="NSLogv">
NSLogv()
</ref>
to print an error message built from the supplied
arguments, and then raising an
NSInternalInconsistencyException
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>handleFailureInMethod:</sel>
<arg type="SEL">aSelector</arg>
<sel>object:</sel>
<arg type="id">object</arg>
<sel>file:</sel>
<arg type="NSString*">fileName</arg>
<sel>lineNumber:</sel>
<arg type="NSInteger">line</arg>
<sel>description:</sel>
<arg type="NSString*">format</arg>
<vararg />
<desc>
Handles an assertion failure by using
<ref type="function" id="NSLogv">
NSLogv()
</ref>
to print an error message built from the supplied
arguments, and then raising an
NSInternalInconsistencyException
</desc>
</method>
</class>
</chapter>
<chapter>
<heading>
Software documentation for the NSException class
</heading>
<class name="NSException" super="NSObject" ovadd="1.0.0">
<declared>Foundation/NSException.h</declared>
<conform>NSCoding</conform>
<conform>NSCopying</conform>
<desc>
<p>
The <code>NSException</code> class helps manage errors
in a program. It provides a mechanism for lower-level
methods to provide information about problems to
higher-level methods, which more often than
not, have a better ability to decide what to do about
the problems.
</p>
<p>
Exceptions are typically handled by enclosing a
sensitive section of code inside the macros
<code>NS_DURING</code> and <code>NS_HANDLER</code>,
and then handling any problems after this, up to the
<code>NS_ENDHANDLER</code> macro:
</p>
<example>
NS_DURING
code that might cause an exception
NS_HANDLER
code that deals with the exception. If this code cannot deal with
it, you can re-raise the exception like this
[localException raise]
so the next higher level of code can handle it
NS_ENDHANDLER
</example>
<p>
The local variable <code>localException</code> is the
name of the exception object you can use in the
<code>NS_HANDLER</code> section. The easiest way to
cause an exception is using the
<ref type="method" id="+raise:format:,...">
+raise:format:,...
</ref>
method.
</p>
<p>
If there is no NS_HANDLER... NS_ENDHANDLER block
enclosing (directly or indirectly) code where an
exception is raised, then control passes to the
<em>uncaught exception handler</em> function and the
program is then terminated. <br /> The uncaught
exception handler is set using
<ref type="function" id="NSSetUncaughtExceptionHandler">
NSSetUncaughtExceptionHandler()
</ref>
and if not set, defaults to a function which will
simply print an error message before the program
terminates.
</p>
</desc>
<method type="NSException*" factory="yes" ovadd="1.0.0">
<sel>exceptionWithName:</sel>
<arg type="NSString*">name</arg>
<sel>reason:</sel>
<arg type="NSString*">reason</arg>
<sel>userInfo:</sel>
<arg type="NSDictionary*">userInfo</arg>
<desc>
Create an an exception object with a <var>name</var>
, <var>reason</var> and a dictionary <var>userInfo</var>
which can be used to provide additional information
or access to objects needed to handle the exception.
After the exception is created you must
<ref type="method" id="-raise">
-raise
</ref>
it.
</desc>
</method>
<method type="void" factory="yes" ovadd="1.0.0">
<sel>raise:</sel>
<arg type="NSString*">name</arg>
<sel>format:</sel>
<arg type="NSString*">format</arg>
<vararg />
<desc>
Creates an exception with a <var>name</var> and a
reason using the <var>format</var> string and any
additional arguments. The exception is then
<em>raised</em> using the
<ref type="method" id="-raise">
-raise
</ref>
method.
</desc>
</method>
<method type="void" factory="yes" ovadd="1.0.0">
<sel>raise:</sel>
<arg type="NSString*">name</arg>
<sel>format:</sel>
<arg type="NSString*">format</arg>
<sel>arguments:</sel>
<arg type="va_list">argList</arg>
<desc>
Creates an exception with a <var>name</var> and a
reason string using the <var>format</var> string and
additional arguments specified as a variable
argument list <var>argList</var>. The exception is
then <em>raised</em> using the
<ref type="method" id="-raise">
-raise
</ref>
method.
</desc>
</method>
<method type="NSArray*" ovadd="10.5.0" gvadd="1.15.1">
<sel>callStackReturnAddresses</sel>
<desc>
Returns an array of the call stack return addresses
at the point when the exception was raised. Re-raising
the exception does not change this value.
</desc>
</method>
<method type="NSArray*" ovadd="10.6.0" gvadd="1.19.3">
<sel>callStackSymbols</sel>
<desc>
Returns an array of the symbolic names of the call
stack return addresses. Note that, on some platforms,
symbols are only exported in position-independent
code and so these may only return numeric addresses
for code in static libraries or the main application.
</desc>
</method>
<method type="id" init="yes" ovadd="1.0.0">
<sel>initWithName:</sel>
<arg type="NSString*">name</arg>
<sel>reason:</sel>
<arg type="NSString*">reason</arg>
<sel>userInfo:</sel>
<arg type="NSDictionary*">userInfo</arg>
<desc>
Initializes a newly allocated NSException
object with a <var>name</var>, <var>reason</var> and
a dictionary <var>userInfo</var>.
</desc>
</method>
<method type="NSString*" ovadd="1.0.0">
<sel>name</sel>
<desc>
Returns the name of the exception.
</desc>
</method>
<method type="void" ovadd="1.0.0">
<sel>raise</sel>
<desc>
Raises the exception. All code following the raise
will not be executed and program control will be
transfered to the closest calling method which
encapsulates the exception code in an
NS_DURING macro. <br /> If the exception was not
caught in a macro, the currently set uncaught
exception handler is called to perform final
logging and the program is then terminated. <br />
If the uncaught exception handler fails to terminate the
program, then the default behavior is to terminate
the program as soon as the uncaught exception handler
function returns. <br /> NB. all other exception
raising methods call this one, so if you want to
set a breakpoint when debugging, set it in this method.
</desc>
</method>
<method type="NSString*" ovadd="1.0.0">
<sel>reason</sel>
<desc>
Returns the exception reason.
</desc>
</method>
<method type="NSDictionary*" ovadd="1.0.0">
<sel>userInfo</sel>
<desc>
Returns the exception userInfo dictionary. <br />
</desc>
</method>
</class>
</chapter>
</body>
</gsdoc>
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