From: Devin Mullins <twifkak@...>
Date: 2005-09-15T11:52:07+09:00
Subject: Re: params v.s. @params in rails?

Ron Jeffries wrote:

>David, Chet Hendrickson and I are just getting back to Ruby after too long away,
>and we've just started working through the Rails book. Mostly happy so far,
>though we're just a couple of days in.
>
>One thing that confused me was the validate method in the first example. I'm
>sure I'm missing something really obvious, but I'd rather be embarrassed than
>confused. ;-> The validate is:
>
>  def validate
>    errors.add(:price, "should be positive") unless price.nil? || price >= 0
>  end
>
>I don't see how "price" canrefer to the field in the record, unless price
>isperhaps an accessor kind of method. But in the class definition, I don't see
>any declaration of a price method.
>
>If it's not too much trouble, since we seem to be close to the topic ... what's
>up with that? How does that access to price work?
>  
>
Ron,

I'm nowhere near a Rails expert, and I'm definitely not David, but I do 
own the book, and the example you're referring to (page 62) says that 
this code goes in the model object. In the model object, yes, price is a 
method invocation on self (a Product object) that returns the content of 
the price column for that row. In Ruby, any undecorated symbolic 
reference 'whatever' looks for a local variable first, and if not 
defined? whatever, calls self.whatever.

If you're pulling up script/console and doing a Product.instance_methods 
and not finding "price" listed, don't fret. It's most likely using 
Product#method_missing (i.e. #doesNotUnderstand).

Hope that answers your question. Also, hope it's right. :)

Devin