CODEWITHSUNDEEP
rubyinheritancemetaprogramming
Daniel
Daniel

Reputation: 7172

class inheritiance, changing a class type in ruby from a parent to a child

I have a regular hash

myhash = { :abc => 123 }

and a class

class SpecialHash < Hash

  def initialize arg_hash
     # how do I say
     self = arg_hash
  end

end

or

Is there some way of doing: myhash.class = SpecialHash?

-daniel

Upvotes: 1

Views: 54

Answers (1)

Simone Carletti
Simone Carletti

Reputation: 176362

The best solution depends on the library you want to extend and on what you are trying to achive.

In case of a Hash, it's quite hard to extend it in that way because there is no initializer you can override when you use the Ruby hash syntax.

However, because creating a new hash with some value is the same of merging an empty hash with the given values, you can do

class SpecialHash < Hash
  def initialize(hash)
     self.merge!(hash)
  end
end

myhash = SpecialHash.new(:abc => 123)

myhash will then be an instance of SpecialHash with the same properties of a Hash.

Notice the use of merge! that is actually changing the value of self. Using self.merge will not have the same effect.

Upvotes: 1

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