From: Stefano Crocco <stefano.crocco@...>
Date: 2009-06-18T01:33:02+09:00
Subject: Re: private method - Fixnum (NoMethodError)

On Wednesday 17 June 2009, salai wrote:
> |Dear All,
> |
> |I can't find the error in my code. Can you explain me "private method
> |-  Fixnum (NoMethodError)"?
> |
> |Many thanks in advance,
> |
> |koko
> |
> |def subtotal(qty = 1)
> |	return nil if self.to_f <= 0 || qty.to_f <= 0
> |	self.to_f * qty.to_f
> |end
> |
> |apple = 11
> |
> |puts apple.subtotal(2)

First of all, when you ask about an error, it's better to report the whole 
error message, not just a bit of it. At any rate, running your code I get the 
error message:

private method `subtotal' called for 11:Fixnum (NoMethodError)

this means that you're calling a private method in a forbidden way, that is 
using the object.method_name notation. Private methods can only be called on 
the explicit receiver (self). Now you may be asking, "why subtotal is a 
private method?" The answer is that methods defined toplevel (that is, methods 
which aren't defined inside a module or a class and aren't singleton methods) 
automatically become private methods of class Object, so you can't call them 
with an explicit receiver.

You have at least two options to fix your code, depending on what exactly you 
need. You can:
1) define your subtotal method like this:
  def subtotal( arg1, qty=1)
    return nil if arg1.to_f <= 0 || qty.to_f <= 0
    arg1.to_f * qty.to_f
  end

and transform apple from the explicit receiver of the call to the first 
argument to subtotal:

  puts subtotal(apple, 2)

2) define the subtotal method in a class. For example, you can define it for 
the Fixnum class:

  class Fixnum
    def subtotal(qty = 1)
      return nil if self.to_f <= 0 || qty.to_f <= 0
       self.to_f * qty.to_f
    end
  end

  then you can call it as you originally did:
  puts apple.subtotal(2)

I hope this helps

Stefano