Ruby Custom Super Initialization

Question

Here is my situation:

• XMLRPC::Client has a proxy constructor, new3, that takes a hash of options. It takes out the individual values to then delegate the construction to the default initializer, initialize
• I am deriving from XMLRPC::Client. I want a class that is XMLRPC::Client but with some added functionality.
• I want to be able to instantiate this derived class using a hash of options as well. This means that in my derived class' initializer, I have to somehow instantiate super using the new3 proxy constructor.

My Question Is if this is possible. If not, then is the only way to solve this is to practically 'copy and paste' the code within the XMLRPC::Client.new3 method into my derived class' constructor?

The reason I'm asking this is simply to see if there is a way of solving this problem, since there is this recurring theme of DRY (Don't Repeat Yourself) within the Ruby community. But of course, if this is the only way, it wont kill me.

Answer 1

I am only posting an answer supplement the other answers by showing you how XMLRPC's code is written

def new3(hash={})

      # convert all keys into lowercase strings
      h = {}
      hash.each { |k,v| h[k.to_s.downcase] = v }

      self.new(h['host'], h['path'], h['port'], h['proxy_host'], h['proxy_port'], h['user'], h['password'],
               h['use_ssl'], h['timeout'])
    end

http://www.ensta.fr/~diam/ruby/online/ruby-doc-stdlib/libdoc/xmlrpc/rdoc/classes/XMLRPC/Client.html

Answer 2

Make a new class method in your derived class (much like they did to make new3 in the first place):

class MyDerived < XMLRPC::Client
    def self.new3(hashoptions)
         client = XMLRPC::Client.new3(hashoptions)
         # Do further initialisation here.
    end
end

myone = MyDerived.new3(:abc => 123, ...)

super only works in initialize (and only changes the parameters to the superclass's initialize), so it doesn't apply here.

Answer 3

You should probably be able to call new3 on you subclass

class MyClient < XMLRPC::Client
end
MyClient.new3({})

Or overwrite it if you need to do extra stuff:

class MyClient < XMLRPC::Client
  def self.new3(args)
    client = super(args)
    # do some more stuff
    client
  end
end
MyClient.new3({})