From: Trans <transfire@...>
Date: 2005-08-31T14:41:26+09:00
Subject: Re: More elegant replacement for global variables


Michael wrote:
> I'm playing around with a ruby app using XML-RPC. Currently I'm using
> global variables so I can create multiple objects without having to log
> in for each and every object.
>
> class Base
> 	def initialize(user, pass)
> 		$user, $pass = user, pass
> 	end
>
> 	def login()
> 		$client = XMLRPC::Client.new(...)
> 		$sessionid = $client.call("xmlrpc.method", $user, $pass)
> 		return $sessionid
> 	end
> end
>
> Derived classes look like this:
>
> class Object1 < Base
> 	def initialize()
> 		if not $sessionid then self.login end
> 	end
> end
>
> This way I can log in once with the first object created without having
> to log in each time. However, this seems inelegant to me. Is there a
> more elegant, or just more rubyish, way of doing this? Also, I'd have
> potential problems if I wanted to log on as multiple users.
>
> Would it make more sense just to pass around an instance of the Base object:
>
> class Object2
> 	def initialize(xmlrpc_client)
> 		if not xmlrpc_client.sessionid then xmlrpc_client.login
> 	end
>
> 	def call_xmlrpc_method(method, params)
> 		results = xmlrpc_client.call(method, params)
> 		return results
> 	end
> end
>
> xmlrpc_client = Base.new
> o2 = Object2.new(xmlrpc_client)
>
> Pro: no global variables. Con: coupling between Object2 and Base classes.
> --Michael

Avoid globals by using container classes/modules. In your cace you
might use the base class itself.

   class Base
     class << self
       attr_accessor :user, :pass
       attr_reader :client, :sessionid
       def login(user=nil,pass=nil)
         @user = user if user
         @pass = pass if pass
         @client = XMLRPC::Client.new(...)
 	 @sessionid = @client.call("xmlrpc.method", @user, @pass)
         return @sessionid
       end
     end

     def initialize
       if not self.class.sessionid then self.class.login end
     end
   end

   class Object1 < Base
     def initialize()
       super
     end
   end

Then use

   Base.login('name','password')

or

   Base.user = 'name'
   Base.pass = 'password'
   Base.login

And go from there. Hope I understood the intent of your code correctly.

T.