Being a Ruby noob (and having a background in Groovy), I was a little surprised that you can not access hash objects using the dot notation.  I am writing an application that relies heavily on XML and JSON data.  This data will need to be displayed and I would rather use book.author.first_name over book[‘author’][‘first_name’].  A quick search on google yielded this post on the subject.

So, taking the DRYOO (Don’t Repeat Yourself Or Others) concept.  I came up with this:

class ::Hash

  # add keys to hash
  def to_obj
    self.each do |k,v|
      if v.kind_of? Hash
        v.to_obj
      end
      k=k.gsub(/\.|\s|-|\/|\'/, '_').downcase.to_sym

      ## create and initialize an instance variable for this key/value pair
      self.instance_variable_set("@#{k}", v)

      ## create the getter that returns the instance variable
      self.class.send(:define_method, k, proc{self.instance_variable_get("@#{k}")})

      ## create the setter that sets the instance variable
      self.class.send(:define_method, "#{k}=", proc{|v| self.instance_variable_set("@#{k}", v)})
    end
    return self
  end
end

This works pretty well.  It converts each of your keys to properties of the Hash. 

However, it doesn’t sit very well with me because I probably will not use 90% of the properties most of the time.  Why should I go through the performance overhead of creating instance variables for all of the unused ones?

Enter the ‘magic method’ #missing_method:

class ::Hash
  def method_missing(name)
    return self[name] if key? name
    self.each { |k,v| return v if k.to_s.to_sym == name }
    super.method_missing name
  end
end

This is a much cleaner method for my purposes.  Quite simply, it checks to see if there is a key with the given symbol, and if not, loop through the keys and attempt to find one.

I am a Ruby noob, so if there is something I am overlooking, please let me know.

Bookmark and Share