Is @selector(foo:) constant?

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3 total messages Started by Ian Flanigan Fri, 21 Aug 1992 18:08

#1265

Author: Ian Flanigan
Date: Fri, 21 Aug 1992 18:08

24 lines
1236 bytes

Today I was trying to manually initialize an array that would associate a bunch  
of selectors.  I tried:

static unsigned int my_array[][3] =
{
   { 1, @selector(foo:), @selector(bar) },
   ...
}

The compiler came back and said:
   initializer for static variable is not constant
So I tried making it non-static.  No good.  (Didn't think it would help :-)  It  
therefore appears that @selector(foo:) does not generate something constant.   
Does anyone know what it _does_ generate?  Anyone have a better idea than to  
use strings and sel_getUid() instead?

Thanks.

--
Ian Flanigan		"You can never have too many napkins."

Project Zeus
Washington University in St. Louis
flan@starling.wustl.edu

Re: Is @selector(foo:) constant?

#1269

Author: Mike Dixon
Date: Sat, 22 Aug 1992 00:42

32 lines
1260 bytes

>    I tried:
>
>	static unsigned int my_array[][3] =
>	{
>	   { 1, @selector(foo:), @selector(bar) },
>	   ...
>        }
>
>    The compiler came back and said:
>       initializer for static variable is not constant

the trick is that although @selector(foo:) isn't constant, &@selector(foo:)
is.  initialize your array with the addresses of the selectors, and
remember to dereference them before you use them.  for example, here's
some code from XText:

  typedef struct {
	  SEL   *sel;
	  short arg1;
	  short arg2;
	  keyCode key;
  } tbl_entry;

  const tbl_entry emacs_base[] = {
    {&@selector(moveChar:mode:), -1,  0, 0x351},  // ctrl-b    move back char
    {&@selector(moveChar:mode:), -1,  1, 0x401},  // ctrl-h  delete back char

                ... etc.

--

                                             .mike.

Re: Is @selector(foo:) constant?

#826

Author: Mike Dixon
Date: Tue, 25 Aug 1992 21:35

19 lines
1200 bytes

** 3.0 Incompatibility Alert! **

a few days ago i wrote:

    the trick is that although @selector(foo:) isn't constant,
    &@selector(foo:) is.  initialize your array with the addresses of
    the selectors, and remember to dereference them before you use
    them.

while this was true in 2.0, a new version of the TextORama MiniExample
that appeared today in the archives suggests that it's no longer true
in 3.0 (i'm not a beta tester, so i can't confirm it).  it appears
that even the addresses of @selector expressions are no longer
constant; to make this kind of code work in 3.0 you'll have to build
the array at runtime (with calls to sel_getUid -- see the new
TextORama for details).
--

                                             .mike.

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