From: Ross Bamford <rossrt@...>
Date: 2006-05-14T16:36:57+09:00
Subject: Re: "Seeing Metaclasses Clearly"

On Sun, 2006-05-14 at 15:28 +0900, Pat Maddox wrote:
> I saw a link for why's article "Seeing Metaclasses Clearly" [1]
> earlier this week.  Been looking at it, and honestly I can't say it's
> making things more clear for me.  The final example is:
> 
>  class MailTruck
>    def self.company( name )
>      meta_def :company do; name; end
>    end
>  end
> 
>  class HappyTruck < MailTruck
>    company "Happy's -- We Bring the Mail, and That's It!"
>  end
> 
> I simply don't see how that's different from
> 
> class MailTruck
>   def self.company(name)
>     instance_eval do
>       define_method(name) { name }
>     end
>   end
> end
> 

I'm sure this is probably a typo, but the above code isn't doing exactly
what it's supposed to:

class HappyTruck < MailTruck
  company "Happy's -- We Bring the Mail, and That's It!"
end

puts HappyTruck.instance_methods
# dup
# hash
# private_methods
# [...]
# Happy's -- We Bring the Mail, and That's It!
# [...]

puts HappyTruck.new.send("Happy's -- We Bring the Mail, and That's It!")
# Happy's -- We Bring the Mail, and That's It!

I.e. you're making an instance method named for the argument passed into
the class-level 'company'. ruby is pretty relaxed about that, but
obviously it can't be called without using send.

Switching to 'define_method(:company) { name }' made it work as (I
think) _why intended.

-- 
Ross Bamford - rosco@roscopeco.REMOVE.co.uk