Can one pass variables through a selector?

[Andrew Hunter]

In article <clund-50F2A4.12443709092003@amstwist00.chello.com>, C Lund wrote:

> Assuming the following declarations:
>
> SEL selectorName;
>
> -(void)aCoordi:(int)iCoord j:(int)jCoord;
> -(void)bCoordi:(int)iCoord j:(int)jCoord;
> -(void)cCoordi:(int)iCoord j:(int)jCoord;
>
> And the above are called by:
>
> [self performSelector:selectorName];
>
> Is there any way to pass iCoord and jCoord through the selector or
> would I have to make iCoord and jCoord global (within the class)? I
> suspect the latter, but I'm asking just in case it can be done.

Yes - either use an NSInvocation to perform the call, or call objc_msgSend()
directly. NSInvocation is the 'official' way to do it, and is mentioned
in the docs for performSelector:.

Andrew.

[Doc O'Leary]

In article <clund-50F2A4.12443709092003@amstwist00.chello.com>,
C Lund <clund@NOSPAMnotam02.no> wrote:

> Is there any way to pass iCoord and jCoord through the selector or
> would I have to make iCoord and jCoord global (within the class)? I
> suspect the latter, but I'm asking just in case it can be done.

Look at NSInvocation instead.

[Michael Milvich]

C Lund <clund@NOSPAMnotam02.no> wrote in message news:<clund-50F2A4.12443709092003@amstwist00.chello.com>...

> Assuming the following declarations:
>
> SEL selectorName;
>
> -(void)aCoordi:(int)iCoord j:(int)jCoord;
> -(void)bCoordi:(int)iCoord j:(int)jCoord;
> -(void)cCoordi:(int)iCoord j:(int)jCoord;
>
> And the above are called by:
>
> [self performSelector:selectorName];
>
> Is there any way to pass iCoord and jCoord through the selector or
> would I have to make iCoord and jCoord global (within the class)? I
> suspect the latter, but I'm asking just in case it can be done.

Take a look at NSInvocation. Basicly you need to follow these steps:

1) Convert your SEL into NSMethodSignature using -methodSignatureForSelector:
2) Create an NSInvocation object using that method signature
3) Set the arguments in the invocation object using -setArgument:atIndex:
4) Send invokeWithTarget: to the invocation object

Michael

[Michael Ash]

In article <clund-50F2A4.12443709092003@amstwist00.chello.com>,
C Lund <clund@NOSPAMnotam02.no> wrote:

> Assuming the following declarations:
>
> SEL selectorName;
>
> -(void)aCoordi:(int)iCoord j:(int)jCoord;
> -(void)bCoordi:(int)iCoord j:(int)jCoord;
> -(void)cCoordi:(int)iCoord j:(int)jCoord;
>
> And the above are called by:
>
> [self performSelector:selectorName];
>
> Is there any way to pass iCoord and jCoord through the selector or
> would I have to make iCoord and jCoord global (within the class)? I
> suspect the latter, but I'm asking just in case it can be done.

You can just do [object performSelector:@selector(aCoordi:j:)
withObject:iCoord withObject:jCoord]. This is a hack, because you're
relying on the fact that you can treat integers as objects if you don't
send messages to them, in current incarnations of Mac OS X. This will
break if you compile for a hypothetical 64-bit version of OS X which
would have 64-bit pointers. PerfomSelector:withObject:withObject:
doesn't send messages, it just passes them along, but that's also
somewhat dangerous to rely on.

Otherwise, you can simply do objc_msgSend(object, @selector(aCoordi:j:),
iCoord, jCoord). Whevere you send a message with [] it gets pretty much
directly translated to a call to objc_msgSend() anyway.

IMO using NSInvocation for this is overkill.

[C Lund]

In article <mail-6B537B.23515709092003@localhost>,
Michael Ash <mail@mikeash.com> wrote:

> You can just do [object performSelector:@selector(aCoordi:j:)
> withObject:iCoord withObject:jCoord]. This is a hack, because you're
> relying on the fact that you can treat integers as objects if you don't
> send messages to them, in current incarnations of Mac OS X. This will
> break if you compile for a hypothetical 64-bit version of OS X which
> would have 64-bit pointers.

Wouldn't a recompile for a 64-bit OS fix it again?

BTW: Thanks for all the answers to my question. B)

--
C Lund, [url]www.notam02.no/~clund[/url]

[Michael Milvich]

C Lund <clund@NOSPAMnotam02.no> wrote in message news:<clund-017CFA.10003810092003@amstwist00.chello.com>...

> In article <mail-6B537B.23515709092003@localhost>,
> Michael Ash <mail@mikeash.com> wrote:
>

> > You can just do [object performSelector:@selector(aCoordi:j:)
> > withObject:iCoord withObject:jCoord]. This is a hack, because you're
> > relying on the fact that you can treat integers as objects if you don't
> > send messages to them, in current incarnations of Mac OS X. This will
> > break if you compile for a hypothetical 64-bit version of OS X which
> > would have 64-bit pointers.

>
> Wouldn't a recompile for a 64-bit OS fix it again?

No it wouldn't. Its a hack because a 32 bit pointer looks just like a
32 bit integer. As long as you don't dereference the pointer everyone
is happy. When you recompile for 64-bit it will create a stack frame
with two 64 bit pointers or 128 bits worth of data, where your method
was only expecting two 32 bit ints or 64 bits of data. I suppose you
could change everything to longs and pass around 64 bit integers, but
that is weak.

Michael