From: Lyle Johnson <lyle@...>
Date: 2002-09-20T14:20:31+09:00
Subject: Re: Attribute Access Problems

Matthew, Graeme wrote:

> I'm just not getting this!

Don't Panic!

> What am I doing wrong here, this is taking way to long :-(
> 
> c:/dev/cgi-bin/Project.rb:80:in `DisplayProject': undefined method
> `projectName' for #<Project:0x25dfae0> (NameError)

OK, I know you can read, but just to clarify: this error message is 
telling you that you're trying to call an instance method named 
"projectName" for the "Project" class, but there is no instance method 
by that name.

> I'm now using instance variables
>  
> def projectName=(val)
> 		@projectName = val if val
> 		return @projectName
> end

This looks fine, but keep in mind that "projectName=()" (a "setter" 
method) and "projectName()" (a "getter" method) are *two* different 
method names...

> but it's failing here in my document:
> 
> <tr><td>Name</td><td><input type="text" name="code"
> value="#{self.projectName}"></td></tr>

Although we can't see all of the code for your "Project" class, I'm 
guessing that you didn't define a "projectName" accessor method to 
complement the "projectName=" method. A quick way to do this (since you 
also have a "@projectName" instance variable) is to use the attr_reader 
method:

     class Project
       attr_reader :projectName
     end

A more verbose (but otherwise equivalent) way to do it is to explicitly 
code-up the method:

     class Project
       def projectName
         @projectName
       end
     end

If you don't already have "Programming Ruby" (a.k.a. the "Pickaxe" book) 
I'd recommend you pick up a copy. It's also available for free online. 
The second chapter:

	http://www.rubycentral.com/book/tut_classes.html

has a section entitled "Objects and Attributes" that does a very nice 
job of explaining what's going on.

Hope this helps,

Lyle