Advantages of using _argument states

Advantages of using _argument states

[Nikolai Weibull]

What are the advantages and disadvantages of using _argument states
over writing functions that generate the matches, i.e,

  '*-chmod[change mode of file]:mode:->modes'

versus

 '*-chmod[change mode of file]:mode:_modes'

(or perhaps __modes to not clutter the Type-completion namespace)?

As far as I can tell, the only difference (and an obvious one at that)
is that states result in a big case-statement but you avoid extra
functions, whereas writing a function adds an extra function, but
saves us from the big case-statement.

I've gone over the documentation a bunch of times and I've been
looking through completion definitions without seeing any point to
using states over functions.

Am I correct in my assessment that they're basically two ways of doing
the same thing and the difference between them is the one I wrote
about above?

Also, writing a function makes it easier to turn that into a Type
completion later on, if need be.

(By the way, I'm writing a completion definition for mkisofs and growisofs.)

Thanks!

  nikolai

Re: Advantages of using _argument states

[Peter Stephenson]

"Nikolai Weibull" <now@bitwi.se> wrote:
> As far as I can tell, the only difference (and an obvious one at that)
> is that states result in a big case-statement but you avoid extra
> functions, whereas writing a function adds an extra function, but
> saves us from the big case-statement.
>
> I've gone over the documentation a bunch of times and I've been
> looking through completion definitions without seeing any point to
> using states over functions.
>
> Am I correct in my assessment that they're basically two ways of doing
> the same thing and the difference between them is the one I wrote
> about above?

There's no hidden piece of magic in states beyond what's documented, no.
Potentially they allow more complicated logic inline:

  _arguments 'blah:blah:->blahstate' && return 0

  blah blah blah any old stuff

  case $state in
    (blahstate)
    blah blah && return 0  # could run _blah here, of course
    ;;
  esac

  blah blah some other stuff

If you'd used a function then you'd have had to bury the extra logic
in the function or at the end of the _arguments line (_alternative or
whatever).  If your particular case doesn't have any of these complications
then a function is probably neater.

--
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070


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