I think that maybe your post got cut off. Either try to re-post or just send me an email at dwischus [at] flexonrails [dot] net.

Derek

*** The Actors ***

Sql Tables
———-
table people
id: int auto-increment pk
name: varchar

table groups
id: int auto-increment pk
name: varchar

table groups_people
group_id: int pk
person_id: int pk

Ruby Model Classes
——————
class Person

Cheers,

Joel

The model (ActiveRecord) knows which issue belongs to which user because that is the info that is stored in the join table.

So if you have,

class Book < ActiveRecord::Base
has_and_belongs_to_many :users
end

and

class User < ActiveRecord::Base
has_and_belongs_to_many :books
end

then following the Rails convention for join tables (i.e., classes1_classes2) you will have a table in your database called,

books_users

books_users has two columns,

book_id
user_id

Ok, so now if you do the following,
@user = User.find(:first)
@books = @user.books

when you call @user.books Rails figures out a whole lot of things based on convention. First it checks the id of User model instance that was returned by User.find(:first). Then it looks for a table called books_users and finds all of the ones where the user_id value matches the id of the current user. Then it grabs the the value stored in book_id for each of these. Lastly, it searches through the books table for books whose id are in the list of book_ids and returns these as Book model instances to @books. See all of the hard work that ActiveRecord is doing for you?

Derek

In my case I am making a book library and sharing application. A user (UserVO) enters a book (BookVO). I have corresponding tables for each. Of course, lots of users might own a single book, so I don’t want multiple entries for twins. Initially I have put a User_ID field in each BookVO, but this locks the book to the user that first input the book. So without a join table in the middle keeping track of these relationships, I just can’t wrap my brain around it.