From: Robert Klemme <shortcutter@...>
Date: 2007-03-04T00:10:09+09:00
Subject: Re: define a function inside a method

On 03.03.2007 15:41, Olivier Renaud wrote:
> Hi,
> 
> I wrote a method which uses recursion, internally. As a test, I tried to 
> define the recursive function inside the method that is called :
> 
> class Ga
>   def bu
>     def zo(n)
>       # recursively call zo
>     end
>   10.times {|n| zo(n)}
> end
> 
> At my surprise, this code ran well ! But I wonder if this is a good idea... 
> Should I be aware of possible problems, or limitations,  coming from this 
> kind of construction ? I can't figure out where the zo function 
> actually "lives".

The issue here is (apart from the missing "end" in your piece above) 
that zo will be defined every time you execute bu - that's probably not 
something you want as it is inefficient and you do not actually change 
zu's definition.  Also, zo becomes a normal method - there is no such 
thing as a nested method in Ruby:

irb(main):001:0> class Ga
irb(main):002:1>   def bu
irb(main):003:2>     def zo(n)
irb(main):004:3>       # recursively call zo
irb(main):005:3*     end
irb(main):006:2>   10.times {|n| zo(n)}
irb(main):007:2> end
irb(main):008:1> end
=> nil
irb(main):009:0> Ga.new.zo 1
NoMethodError: undefined method `zo' for #<Ga:0x39ba98>
         from (irb):9
         from :0
irb(main):010:0> Ga.new.bu
=> 10
irb(main):011:0> Ga.new.zo 1
=> nil

Kind regards

	robert