delegates - Ruby: DRY class methods calling Singleton instance methods -

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• calling method of ruby singleton without reference of 'instance' 4 answers

i have singleton class exchangeregistry keeps exchange objects.

instead of needing call: exchangeregistry.instance.exchanges

i want able use: exchangeregistry.exchanges

this works, i'm not happy repetition:

require 'singleton'  # ensure exchange created once class exchangeregistry   include singleton    # class methods  ###### here duplication , dragons    def self.exchanges     instance.exchanges   end    def self.get(exchange)     instance.get(exchange)   end    # instance methods    attr_reader :exchanges    def initialize     @exchanges = {} # stores every exchange created   end    def get(exchange)     @exchanges[exchange.to_sym exchange] ||= exchange.create(exchange)   end end 

i'm not happy duplication in class methods.

i've tried using forwardable , simpledelegator can't seem dry out. (most examples out there not class methods instance methods)

the forwardable module this. since forwarding class methods, have open eigenclass , define forwarding there:

require 'forwardable' require 'singleton'  class foo    include singleton    class << self     extend forwardable     def_delegators :instance, :foo, :bar   end    def foo     'foo'   end    def bar     'bar'   end  end  p foo.foo    # => "foo" p foo.bar    # => "bar"