From: Stefano Crocco <stefano.crocco@...>
Date: 2009-08-27T18:18:03+09:00
Subject: Re: A bizarre problem with data= methods

On Thursday 27 August 2009, David Espada wrote:
> |Hi all.
> |
> |I have found an error that does not understand. Look this simple code:
> |
> |---------------------------------
> |class Foo
> |  def value=(data)
> |    puts "Look #{data}"
> |  end
> |end
> |
> |f = Foo.new.value = "at me" # => Look at me
> |---------------------------------
> |
> |Great! A little assigner that works perfectly. But now I make a
> |constructor that use the assigner directly:
> |
> |---------------------------------
> |class Foo
> |  def initialize(data)
> |    value = data
> |  end
> |
> |  def value=(data)
> |    puts "Look #{data}"
> |  end
> |end
> |
> |f = Foo.new("at me") # => Nothing!!!!!!!!!
> |---------------------------------
> |
> |Why? The constructor doesn't use value= method. What is happening? Is
> |that normal?
> |
> |Thanl you for your help.
> |

Because when ruby sees something like:

identifier = value

it thinks you're creating a local variable called identifier, not calling the 
identifier= method. To force ruby to understand you want to call the method, 
you need to use the dot notation, self.identifier = value, or use send: 
send(:identifier=, value).

I hope this helps

Stefano