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Authors
- Adam Fedor (
fedor@boulder.colorado.edu
)
-
Version: 23921
Date: 2006-10-20 04:56:27 -0600 (Fri, 20 Oct 2006)
Copyright: (C) 1995, 1996 Free Software Foundation, Inc.
- Declared in:
- Foundation/NSException.h
Availability: OpenStep
NSAssertionHandler objects are used to
raise exceptions on behalf of macros implementing
assertions.
Each thread has its own
assertion handler instance.
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.
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.
The assertion macros are:
NSAssert()
, NSCAssert()
,
NSAssert1()
, NSCAssert1()
,
NSAssert2()
, NSCAssert2()
,
NSAssert3()
, NSCAssert3()
,
NSAssert4()
, NSCAssert4()
,
NSAssert5()
, NSCAssert5()
,
NSParameterAssert()
,
NSCParameterAssert()
Method summary
+ (
NSAssertionHandler*)
currentHandler;
Availability: OpenStep
Returns the assertion handler object for the
current thread.
If none exists, creates one
and returns it.
- (void)
handleFailureInFunction: (
NSString*)functionName
file: (
NSString*)fileName
lineNumber: (int)line
description: (
NSString*)format
,...;
Availability: OpenStep
Handles an assertion failure by using
NSLogv()
to print an error message built from the supplied
arguments, and then raising an
NSInternalInconsistencyException
- (void)
handleFailureInMethod: (SEL)aSelector
object: (id)object
file: (
NSString*)fileName
lineNumber: (int)line
description: (
NSString*)format
,...;
Availability: OpenStep
Handles an assertion failure by using
NSLogv()
to print an error message built from the supplied
arguments, and then raising an
NSInternalInconsistencyException
- Declared in:
- Foundation/NSException.h
- Conforms to:
- NSCoding
- NSCopying
Availability: OpenStep
The NSException
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.
Exceptions are typically handled by enclosing a
sensitive section of code inside the macros
NS_DURING
and NS_HANDLER
,
and then handling any problems after this, up to the
NS_ENDHANDLER
macro:
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
The local variable localException
is the
name of the exception object you can use in the
NS_HANDLER
section. The easiest way to
cause an exception is using the
+raise:format:,...
method.
If there is no NS_HANDLER... NS_ENDHANDLER block
enclosing (directly or indirectly) code where an
exception is raised, then control passes to the
uncaught exception handler function and the
program is then terminated.
The uncaught
exception handler is set using
NSSetUncaughtExceptionHandler()
and if not set, defaults to a function which will
simply print an error message before the program
terminates.
Instance Variables
Method summary
+ (
NSException*)
exceptionWithName: (
NSString*)name
reason: (
NSString*)reason
userInfo: (
NSDictionary*)userInfo;
Availability: OpenStep
Create an an exception object with a
name
,
reason and a dictionary
userInfo
which can be used to provide additional information
or access to objects needed to handle the exception.
After the exception is created you must
-raise
it.
+ (void)
raise: (
NSString*)name
format: (
NSString*)format
,...;
Availability: OpenStep
Creates an exception with a
name and a
reason using the
format string and any
additional arguments. The exception is then
raised using the
-raise
method.
+ (void)
raise: (
NSString*)name
format: (
NSString*)format
arguments: (va_list)argList;
Availability: OpenStep
Creates an exception with a
name and a
reason string using the
format string and
additional arguments specified as a variable
argument list
argList. The exception is
then
raised using the
-raise
method.
- (id)
initWithName: (
NSString*)name
reason: (
NSString*)reason
userInfo: (
NSDictionary*)userInfo;
Availability: OpenStep
This is a designated initialiser for the class.
Initializes a newly allocated NSException
object with a name, reason and
a dictionary userInfo.
- (
NSString*)
name;
Availability: OpenStep
Returns the name of the exception.
- (void)
raise;
Availability: OpenStep
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.
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.
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.
NB. all other exception
raising methods call this one, so if you want to
set a breakpoint when debugging, set it in this method.
- (
NSString*)
reason;
Availability: OpenStep
Returns the exception reason.
- (
NSDictionary*)
userInfo;
Availability: OpenStep
Returns the exception userInfo dictionary.
There is a GNUstep extension, enabled when the
GNUSTEP_STACK_TRACE environment
variable is set to YES
, which causes
a stack trace to be placed in this dictionary (keyed on
GSStackTraceKey) at the point when the
exception is raised. This can be useful for
determining where an exception ocurred.
Instance Variables for NSException Class
@protected NSDictionary* _e_info;
Availability: OpenStep
Warning the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically private, it is
intended for internal use within the package, and
you should not use the variable in other code.
@protected NSString* _e_name;
Availability: OpenStep
Warning the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically private, it is
intended for internal use within the package, and
you should not use the variable in other code.
@protected NSString* _e_reason;
Availability: OpenStep
Warning the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically private, it is
intended for internal use within the package, and
you should not use the variable in other code.
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