Method: Lemo::Ormo::ClassMethods#ormo

Defined in:
lib/lemo/ormo.rb

#ormo(meth) ⇒ Object Also known as: memo

WARNING race condition if two threads concurrently define the same memo’ed method on the same class. Unlikely, but still.



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# File 'lib/lemo/ormo.rb', line 25

def ormo( meth )
  unbound_previous_method = instance_method meth

  # still doesn't prevent memoisation of methods with an implicit block
  unless unbound_previous_method.parameters.empty?
    raise ArgumentError, "can't memo #{meth} with parameters"
  end

  # keep this for initial calculation, and recalculation
  memoed_methods[meth] = unbound_previous_method
  ivar = ivar_from meth

  # Define the class using instance variable @ syntax, for fastest
  # runtime. Use class_eval to define an instance method, cos self is the
  # class (or singleton class) right now
  class_eval <<-RUBY, __FILE__, __LINE__
    def #{meth}
      #{ivar} ||= _memoed_methods[:#{meth}].bind(self).call
    end
  RUBY

  # allow chaining of symbol returned from def
  meth
end