From: Robert Klemme <shortcutter@...>
Date: 2009-05-05T15:30:07+09:00
Subject: Re: accessing one class from another class

On 04.05.2009 23:39, Nick da G wrote:
> Hello, All.
> 
> I'm trying to consuming an xml file and map it to a Ruby object that
> would describe that xml file.
> 
> What would be the best way to implement the following scenario.
> 
> Let's say I have several classes: Student, Course, Person, Tuition
> Xml for this would look like this:
> <Record>
> <Student status="good">
>   <Person>
>     <Name>Alice</Name>
>     <BirthPlace>WonderLand</BirthPlace>
>   </Person>
>   <Course difficulty=">
>     <CourseName>Math III</CourseName>
>     <Grade>B+</Grade>
>   </Course>
>   <dt:Tuition>
>     <dt:Currency>USD</dt:Currency>
>     <dt:Amount>500</dt:Amount>
>     <dt:Period>3 months</dt:Period>
>   </dt:Tuition>
> </Student>
> </Record>
> So basically I can parse the xml file using rexml and access all of my
> xml tags and stuff.
> 
> Here is the Object I want to map it to:
> 
> 
> class Student
>  @status
>  @person - access Person
> end
> 
> class Person
> end
> 
> class Course
> end
> 
> class Tution
> end
> 
> 
> 
> So the question is how do I access from class Student - class Person? So
> that when I down the line later when I parse the file and do:
> 
> r = Record.new
> 
> I want to be able to do things like:
> r.student.person.name

You can define attributes via attr_accessor, e.g.

class Student
   attr_accessor :person
end

class Person
   attr_accessor :name
end

st = Student.new
pe = Person.new
pe.name = "Nick"
st.person = pe

etc.

As a shortcut you can as well use Struct:

Student = Struct.new :person
Person = Struct.new :name

Kind regards

	robert