Module: MultiMethods::ClassMethods

Defined in:
lib/multi_methods.rb

Instance Method Summary collapse

Instance Method Details

#create_method(name, &block) ⇒ Object 



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# File 'lib/multi_methods.rb', line 9

def create_method( name, &block ) 
  self.send( :define_method, name, block )
end

#defmethod(method_name, dispatch_value, default_dispatch_fn) ⇒ Object 



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# File 'lib/multi_methods.rb', line 44

def defmethod method_name, dispatch_value, default_dispatch_fn
  multi_method = self.instance_variable_get( "@" + method_name.to_s)  
  raise "MultiMethod #{method_name} not defined" unless  multi_method
  multi_method << {  dispatch_value => default_dispatch_fn } 
end

#defmulti(method_name, default_dispatch_fn = nil) ⇒ Object 



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# File 'lib/multi_methods.rb', line 13

def defmulti method_name, default_dispatch_fn = nil
  self.instance_variable_set( "@" + method_name.to_s, [] )

  create_method( method_name ) do |*args|
    dispatch_table = self.class.instance_variable_get( "@" + method_name.to_s )

    dispatch_table.each do |m|
      predicate = if m.keys.first.respond_to? :call
                    raise "Dispatch method already defined by defmulti" if default_dispatch_fn
                    m.keys.first
                  elsif  m.keys.first == :default
                    :default
                  else
                    lambda { |args| return default_dispatch_fn.call(args) == m.keys.first }
                  end

      destination_fn = m.values.first

      if predicate == :default  || predicate.call(args)
        if destination_fn.is_a? UnboundMethod
          break destination_fn.bind( self ).call(args)
        else
          break destination_fn.call(args)
        end
        break
      end
      raise "No matching dispatcher function found" if dispatch_table.last == m
    end
  end
end