Re: [sigc] How to use sigc::bind<>

[Martin Schulze <martin-ml hippogriff de>]

Hi!

Thanks for all your input on the subject. I think consensus can be
reached about the sigc::bind() and sigc::hide() API with the following
change I'm about to commit to cvs:

  * sigc++/adaptors/macros/[bind,hide].h.m4: Change to zero-based
  argument index in numbered bind() and hide() overload
  (Agreement on the mailing list).
  Support binding up to CALL_SIZE arguments with one bind adaptor.
  (Requested by joey yandle and others).
  Only support binding of multiple arguments in unnumberd overloads
  to keep the API simple (Requested by Murray Cumming).


Now the sigc::bind() API looks as follows:

  sigc::bind() alters an arbitrary functor by fixing arguments to 
certain values.
  Up to 7 arguments can be bound at a time.
  For single argument binding overloads of sigc::bind() are provided 
that let you
  specify the zero-based position of the argument to fix with the 
first template parameter.
  (A value of @p -1 fixes the last argument so sigc::bind<-1>() gives 
the same result as sigc::bind().)
  The types of the arguments can optionally be specified if not 
deduced.

  Examples:
    void foo(int, int, int);
    // single argument binding ...
    sigc::bind(&foo,1)(2,3);     //fixes the last (third) argument and 
calls foo(2,3,1)
    sigc::bind<-1>(&foo,1)(2,3); //same as bind(&foo,1)(2,3) (calls foo
(2,3,1))
    sigc::bind<0>(&foo,1)(2,3);  //fixes the first argument and calls 
foo(1,2,3)
    sigc::bind<1>(&foo,1)(2,3);  //fixes the second argument and calls 
foo(2,1,3)
    sigc::bind<2>(&foo,1)(2,3);  //fixes the third argument and calls 
foo(2,3,1)
    // multi argument binding ...
    sigc::bind(&foo,1,2)(3);     //fixes the last two arguments and 
calls foo(3,1,2)
    sigc::bind(&foo,1,2,3)();    //fixes all three arguments and calls 
foo(3,1,2)


Cheers!

  Martin


Am 2003.11.11 21:39 schrieb(en) joey yandle:
> >
> > Please do consider not including an API if it can't be done simply.
> Really,
> > who needs to bind more than 1 argument?
> >
>
> I bind multiple arguments quite frequently.  In gtkmail, there's one
> place
> where I have to bind 5 arguments, and it's quite painful given the
> current "only bind two args" usage:
>
>
>             SigC::Slot5<void,std::string,std::string,std::string,
> std::string,unsigned
> int> s5 =
>                 SigC::slot(&jlib::net::smtp::send);
>
>             SigC::Slot3<void,std::string,std::string,std::string> s3;
>
>             std::string smtp_server =
> Config::global.find(m_box->get_name())->get_smtp();
>
>             s3 = SigC::bind(s5,smtp_server,25);
>
>             SigC::Slot1<void,std::string> s1 =
> SigC::bind(s3,rcpt,m_email.raw());
>             SigC::Slot0<void> s0 = SigC::bind(s1,mail);
>
> It would be twice as irritating if I could only bind 1 at a time, and
> much
> more pleasant if I could bind as many as I needed...
>
> --
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