Robert, Thanks so much for the help. Question, though, could you help with with the routing that would be involved?
On Oct 1, 7:20 pm, Robert Walker <[email protected]> wrote: > mlittle wrote: > > Robert, thanks for the reply. validates_existence_of is a plugin -> > >http://github.com/bogdans83/validates_existence_of/. I'll try to make > > this as simple as possible. Here is what i'm trying to do: > > Got it. I though maybe that was the case, and might explain some of my > previous frustrations with testing these associations. > > > A's has many B's and B's have 1 C. > > > A = Users > > B = Books > > C = Libraries > > Okay, That makes more sense. Let me first write this as a user story: > > Users may check out many books from a library. Users may borrow from > many libraries. Only one library may own a book (in this design let's > consider two books with the same title separate books). Books loaned to > users must be returned to the owning library. > > So I see four models here not three: > > User > Library > Book > Loan > > Feature: Book check out > In order to learn cool stuff, or be entertained > As a user > I want to be able to checkout many books from many libraries > > Scenario: Check from 2 libraries > Given I select 'Programming Ruby' from the Public Library > And I select 'The Rails Way' from the University Library > When I check out from the Public Library > And I check out from the University Library > Then I should have 2 books > > Feature: Book check in > In order to prevent late fees > As a user > I want to be able to check in books > > Scenario: I must return a book to the correct library > Given I have 'Programming Ruby' > When I check in to the University Library > Then the check in should be denied > And I should have 2 books > > There may be other scenarios to consider, but I wanted to focus on these > two to help describe the model: > > It looks to me like you need a standard many-to-many association with > some additional validation to make sure the books get returned back to > the library that owns them. > > class User < ActiveRecord::Base > has_many :loans > has_many :books, :through => :loans > end > > class Loan < ActiveRecord::Base > belongs_to :user > belongs_to :book > end > > class Book < ActiveRecord::Base > has_many :loans > has_many :users, :through => :loans > belongs_to :library > end > > class Library < ActiveRecord::Base > has_many :books > end > > loans_controller.rb > > # DELETE /loans/1 > # DELETE /loans/1.xml > def destroy > @loan = Loan.find(params[:id]) > @loan.destroy if @loan.book.library == current_library > > respond_to do |format| > flash[:error] = "This book was > format.html { redirect_to(loans_url) } > format.xml { head :ok } > end > end > > I'll leave it as an exercise for you to figure out how to determine the > "current library" that the user is attempting to return the book to. > > Notice that in this design the act of checking in a book is to destroy > the loan of the book. So loan is a resource in it's own right. Of course > checking out a book would be to create a new loan. > > Note: this code is incomplete and untested with no warrantee of any > kind. :) > -- > Posted viahttp://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
