From: Robert Klemme <bob.news@...>
Date: 2004-10-11T20:24:38+09:00
Subject: Re: [Q] case based on object class


"Robert Klemme" <bob.news@gmx.net> schrieb im Newsbeitrag
news:2sv8kcF1q3732U1@uni-berlin.de...
>
> "George Moschovitis" <gm@navel.gr> schrieb im Newsbeitrag
> news:ckdn7c$2eim$1@ulysses.noc.ntua.gr...
> > > I am not sure what you want to do... do you want to separate these
> > > things by class and print out the corresponding symbol?
> >
> > i want to execute different code depending on the klass (Class) object
> > given to the method.
> >
> > > Anyhow, I tried your code and it worked fine for me. I substituted
> > > 4 for obj and commented the ...  of course.
> >
> > the code works, I am wondering if there is a more elegant/efficient
> > way to write it.
>
> The OO way is to use a mapping IMHO:

I forgot to mention that this is also more efficient if you have many
classes.

> ACTION_MAPPING = {
>   Fixnum => lambda { puts "Fixnum" },
>   Float  => lambda { puts "Float" },
>   String => lambda { puts "String" },
> }
>
> def myfunc(klass)
>   code = ACTION_MAPPING[klass]
>   raise ArgumentError, "Klass not found: #{klass}" unless code
>   code.call
> end
>
> You can even define a block for the error as default effectively
rendering
> the method a one liner like this:
>
> ACTION_MAPPING = Hash.new( lambda { raise ArgumentError, "Klass not
> found" } ).update(
>   Fixnum => lambda { puts "Fixnum" },
>   Float  => lambda { puts "Float" },
>   String => lambda { puts "String" }
> )
>
> def myfunc(klass) ACTION_MAPPING[klass].call end

And then there is also the option to define those methods as singleton
methods of the classes although I recommend to do this *only* if the
functionality is general enough and has to do with the class more than
with your app.

Kind regards

    robert