From: Daniel N <has.sox@...>
Date: 2006-10-09T21:02:07+09:00
Subject: Re: Removing Duplicate Objects from Object List

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On 10/9/06, Jeff Nyman <jeffnyman_nospam@nospam_gmail.com> wrote:
>
> "gaspode" <stephendl@gmail.com> wrote in message
> news:1160393869.844030.8080@m7g2000cwm.googlegroups.com...
>
> > How are you storing the Rules in your RuleSet at the moment? Personally
> > I'd use an Array (or simply subclass Array) and then you get to use
> > Array.uniq without shifting objects back and forth.
>
> Essentially, I have a RuleList class like this:
>
> <code>
> class RuleList
>   def initialize
>     @rules = Array.new
>   end
>
>   def append(this_rule)
>     @rules.push(this_rule)
>   end
>
>   def selection
>     @rules.find_all { |rule| rule }
>   end
> end
> </code>
>
> Then I have a Rule class like this:
>
> <code>
> class Rule
>   attr_accessor :point, :filter, :value
>
>   def initialize(point, filter, value)
>     @point = point
>     @filter = filter
>     @value = value
>   end
>
>   def to_s
>     "#@point, #@filter, #@value"
>   end
> end
> </code>
>
> When a rule object needs to be added to the list, I do this:
>
> $ruleList.append(Rule.new(step.point2, rule, value))
>
> Does that give enough detail?
>
> In playing around a bit more, I tried this:
>
> rules_array = $ruleList.selection.collect { |rule| rule }
>
> Then I tried:
>
> rules_array.uniq!
>
> The problem is that this finds nothing as a duplicate. But that makes
> sense
> (I think) because the object ID is probably being considered as part of
> the
> test and those will, of course, not be duplicates.
>
> It sounds like you're saying it would be better to not use a Rule class in
> the first place. Is that accurate?
>
> - Jeff


If instead of declaring your @rules as an array, you declare it as a set you
will get no duplicates for free (I think)

However,  you need to incorporate the <=> operator in your Rule class to
tell ruby how your objects relate to each other.
ie are they  <, >, or =

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