Marcin Mielzynski
5/11/2007 4:05:00 PM
konryd wrote:
> Hello, I need to add in runtime several methods to my class. How can I
> accomplish this in ruby?
> More precisely: I need my class to overload arithmetic operators with
> fixnums in both ways (4+MyClass, MyClass+4). All the necessary info is
> stored in a hash, so I created a method to do all the stuff. It looks
> like do_operation(operator, other)
> But still I have to add every single operator overloader:
> class Fixnum
>
> def doo_operation(operator, other)
> #...nevermind...
> end
>
> def +(other)
> do_operation(:+, other)
> end
> def -(other)
> do_operation(:-, other)
> end
> end
>
> can I automate it somehow?
>
the simplest case someone might come up with is:
module Operators
def operation operator, other
puts "operator #{operator} with argument #{other} called"
end
OPERATORS = [:+,:-,:/,:*]
def self.included mod
mod.instance_eval do
OPERATORS.each do |op|
begin
instance_method(op)
alias_method(:"_#{op}", op)
rescue
# swallow NameError here
end
define_method op do |other|
# here you might want to check for 'other' class to
preserve Numeric/Enumerable behaviour
operation op, other
end
end
end
end
end
class Fixnum
include Operators
end
1 + 2
1.send :"_+" ,2 # original
class A
include Operators
end
A.new + A.new
lopex