From: "David A. Black" <dblack@...>
Date: 2005-10-28T14:05:07+09:00
Subject: Re: "Reflecting" on my self.n00b

Hi --

On Fri, 28 Oct 2005, swille wrote:

> Still though, I'm unsure of whether this is a smart thing to do.  Any
> thoughts on that?  I'd definitely like to learn the right way to do
> stuff.
>
> class ServiceProfile
>    def  initialize
>        @sp_url = nil
>        @sp_username = nil
>        @sp_password = nil
>        @sp_certificate = nil
>        @sp_owner = nil
>    end
>

That looks kind of odd.  Instance variables default to nil anyway.  If
you're just trying to trigger them into existence, then I think the
program design is probably suspect.

>    def load_certificate
>        @sp_certificate.read
>    end
>
>    def call_service(&block)
>    end

What's that method for?  (It's not actually doing anything.)

> end
>
> class MyService < ServiceProfile
>    def  initialize
>        @sp_extra = nil
>        super
>    end
> end
>
> svc_profile = MyService.new #ServiceProfile.new
> sp_re = Regexp.new('^@sp_(\w+)')
>
> svc_profile.instance_variables.sort.reverse.each { |var|
>    if var.match(sp_re)
>        print "Enter #{Regexp.last_match(1).capitalize}: "
>        value = $stdin.gets.chomp
>        svc_profile.instance_variable_set(var, value)
>    end
> }
>
> svc_profile.instance_variables.sort.reverse.each { |var|
>    if var.match(sp_re)
>        puts svc_profile.instance_variable_get(var)
>    end
> }
>

The thing with the instance variable names matching a regex looks very
fragile.  I would recommend using real data structures.  You could do
something like this:


   class ServiceProfile
     SP_ITEMS = %w{url username password certificate owner }

     def sp_items
       self.class::SP_ITEMS
     end

     def initialize
       @sp_hash = {}
     end

     def save_service(service,value)
       @sp_hash[service] = value
     end
   end

   class MyService < ServiceProfile
     SP_ITEMS = SP_ITEMS.dup
     SP_ITEMS << "extra"
   end

And then you could just use the data structures to get and save your
data:

   svc_profile = MyService.new
   svc_profile.sp_items.each do |item|
     print "Enter #{item.capitalize}: "
     value = gets.chomp
     svc_profile.save_service(item,value)
   end


David

-- 
David A. Black
dblack@wobblini.net