From: Timothy Hunter <cyclists@...>
Date: 2006-02-13T06:48:25+09:00
Subject: Re: How to pass a function as argument in ruby?

the_crazy88 wrote:
> I've searched a bit about the subject, but I don't understand it. All I
> want is to simply pass a function of one instance to another. In Python
> this works, but in ruby not.
> 
> Python code would be:
> def x(a,b):
>   return a+b
> 
> def y(a):
>   return a(3,4)
> 
> y(x)
> # Result is 7
> But the equivalent ruby code doesn't work:
> 
> def a(x,y)
>   return x+y
> end
> 
> def x(b)
>   return b(3,4)
> end
> 
> x(a)
>  #Gives the following error in irb:
> 
> NoMethodError: undefined method `b' for main:Object
>         from (irb):40:in `x'
>         from (irb):42
>         from :0
> 

In Ruby it's typical to encapsulate bits of code in Proc objects and 
pass these objects around:

p = Proc.new {|x,y} x+y}

p.call(2,3) -> 5

If you're really wanting to pass methods around from one instance to 
another, check out the doc for the UnboundMethod class with ri.