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fix documentation error

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git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@27642 72102866-910b-0410-8b05-ffd578937521
This commit is contained in:
Richard Frith-MacDonald 2009-01-20 18:49:23 +00:00
parent 399e2f9b38
commit c1aae0c84c
2 changed files with 20 additions and 6 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2009-01-20 Richard Frith-Macdonald <rfm@gnu.org>
* Documentation/manual/ExceptionHandling.texi: Fix error in
example of use of NS_VALUERETURN spotted by David Chisnall.
2009-01-20 Richard Frith-Macdonald <rfm@gnu.org>
* Source/NSKeyValueObserving.m: Automtically remove collected observers

21
Documentation/manual/ExceptionHandling.texi
View file

@ -86,16 +86,20 @@ For instance:
@{
FileHandle *handle = [self getFileHandle: filename];
parse = [parser parseFile: handle];
if (parse == nil)
@{
NS_VALUERETURN(nil);
@}
@}
NS_HANDLER
@{
if ([[localException name] isEqualToString: MyFileNotFoundException])
@{
NS_VALUERETURN([self readDataFile: fallbackFilename]);
return [self readDataFile: fallbackFilename];
@}
else if ([[localException name] isEqualToString: NSParseErrorException])
@{
NS_VALUERETURN([self readDataFileInOldFormat: filename]);
return [self readDataFileInOldFormat: filename];
@}
else
@{
@ -113,13 +117,18 @@ occur, the code in the @code{NS_HANDLER} block is jumped to. Information on
the error is passed to this code in the @code{localException} variable, which
is an instance of @code{NSException}. The handler code examines the name of
the exception to determine if it can implement a work-around. In the first
two cases, an alternative approach is available, and so the
@code{NS_VALUERETURN} macro is used to return an alternative value to the
two cases, an alternative approach is available, and so an alternative value
is returned.
If the file is found but the parse simply produces a nil parse tree, the
@code{NS_VALUERETURN} macro is used to return nil to the
@code{readDataFile:} caller. Note that it is @i{not} allowed to simply write
``@code{return x;}'' inside an exception handler, owing to the nature of the
``@code{return nil;}'' inside the NS_DURING block, owing to the nature of the
behind-the-scenes C constructs implementing the mechanism (the @code{setjmp()}
and @code{longjmp()} functions). If you are in a void function not returning
a value, you may use simply ``@code{NS_VOIDRETURN}'' instead. Finally, notice
a value, you may use simply ``@code{NS_VOIDRETURN}'' instead.
Finally, notice
that in the third case above the handler does not recognize the exception
type, so it passes it one level up to the caller by calling @code{-raise} on
the exception object.