From: Markus <markus@...>
Date: 2004-10-01T12:34:04+09:00
Subject: Re: Can you rewrite this in a better way?

     No idea if it's "better" but here's one I use:

class Module
    #
    # To automate the reading and writing of objects
    #
    def columns
        @columns ||= []
        end
    private
        def field(*ids)
            @columns ||= []
            ids.each { |id|
                id = id.to_s
                attr_accessor id unless id =~ /\[/ or
instances_respond_to? id+'='
                @columns << id
                }
            end
    end



On Thu, 2004-09-30 at 18:10, Bob Sidebotham wrote:
> I would like to define a method that can be used to compactly define 
> some items of interest (here called "fields") for subclasses. It's used 
> like this:
> 
> class B < A
>    fields :a, :b, :c
> end
> 
> class C < A
>    fields :x, :y
> end
> 
> p B.new.fields                => [:a, :b, :c]
> p C.new.fields                => [:x, :y]
> 
> Here are two definitions for class A that support these semantics:
> 
> ---#1------------------------------------------------
> 
> class A
>    def self.fields(*fields)
>      @fields = fields
>      def fields
>        self.class.getFields
>      end
>    end
> 
>    private
>    def self.getFields
>      @fields
>    end
> end
> 
> ---#2------------------------------------------------
> 
> class A
>    def self.fields(*fields)
>      eval "def fields
>        [#{fields.collect{|f| ':' + f.to_s}.join(',')}]
>      end"
>    end
> end
> 
> -----------------------------------------------------
> 
> Is there a better way (more efficient, shorter and/or clearer) to do this?
> 
> Thanks!
> Bob Sidebotham
>