From: Per-erik Martin <lists@...>
Date: 2013-05-06T18:57:38+09:00
Subject: Re: Hash return is not correct

Ruby Mania wrote in post #1107907:
>
>   def ==(other)
>     return false unless other.is_a?(Router)
>      make == other.make && model == other.model

That should be eql?, and @make/@model:

  def eql?(other)
    return false unless other.is_a?(Router)
    @make.eql?(other.make) && @model.eql?(other.model)
  end


>   end
>

You also need to override the hash method, e.g.:

  def hash()
    @make.hash ^ @model.hash
  end


> end
>
> frequency = Hash.new(0)
> models = %w(2000 3000 2000 3200)
> models.each{|m| frequency[Router.new('Linksys',m)] += 1}
> puts frequency[Car.new('Linksys','2000')]

As noted, should be Router:

  puts frequency[Router.new('Linksys','2000')]

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