Module: Memoized::ClassMethods

Defined in:
lib/memoized.rb

Instance Method Summary collapse

Instance Method Details

#memoize(*method_names) ⇒ Object 



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# File 'lib/memoized.rb', line 16

def memoize(*method_names)
  method_names.each do |method_name|
    memoized_ivar_name = Memoized.ivar_name(method_name)
    unmemoized_method = "_unmemoized_#{method_name}"

    alias_method unmemoized_method, method_name

    arity = instance_method(unmemoized_method).arity

    if arity == 0
      module_eval(<<-RUBY)
        def #{method_name}()
          #{memoized_ivar_name} ||= [#{unmemoized_method}()]
          #{memoized_ivar_name}.first
        end
      RUBY

    elsif arity == -1
      module_eval(<<-RUBY)
        def #{method_name}(*args)
          #{memoized_ivar_name} ||= {}
          if #{memoized_ivar_name}.has_key?(args)
            #{memoized_ivar_name}[args]
          else
            #{memoized_ivar_name}[args] = #{unmemoized_method}(*args)
          end
        end
      RUBY

    elsif arity < -1
      # For Ruby methods that take a variable number of arguments,
      # Method#arity returns -n-1, where n is the number of required arguments
      required_arg_names = (1..(-arity - 1)).map { |i| "arg#{i}" }
      required_args_ruby = required_arg_names.join(', ')

      module_eval(<<-RUBY)
        def #{method_name}(#{required_args_ruby}, *optional_args)
          all_args = [#{required_args_ruby}, *optional_args]
          #{memoized_ivar_name} ||= {}
          if #{memoized_ivar_name}.has_key?(all_args)
            #{memoized_ivar_name}[all_args]
          else
            #{memoized_ivar_name}[all_args] = #{unmemoized_method}(*all_args)
          end
        end
      RUBY

    else # positive arity
      arg_names = (1..arity).map { |i| "arg#{i}" }
      args_ruby = arg_names.join(', ')

      module_eval(<<-RUBY)
        def #{method_name}(#{args_ruby})
          all_args = [#{args_ruby}]
          #{memoized_ivar_name} ||= {}
          if #{memoized_ivar_name}.has_key?(all_args)
            #{memoized_ivar_name}[all_args]
          else
            #{memoized_ivar_name}[all_args] = #{unmemoized_method}(#{args_ruby})
          end
        end
      RUBY
    end

    if self.private_method_defined?(unmemoized_method)
      private method_name
    elsif self.protected_method_defined?(unmemoized_method)
      protected method_name
    end
  end
end