OK, I'm still having some issues with this. Here's what I ended up with in
my migrations:
<<
create_table(:books) do
primary_key :id
String :title
end
create_table(:locations) do
primary_key :id
String :location
end
create_table(:books_locations) do
primary_key :id
foreign_key :location_id, :locations
foreign_key :book_id, :books
Integer :total
Integer :checked_out
end
>>
and my models:
<<
class Book < Sequel::Model
one_to_many :book_locations
many_to_many :locations, :join_table=>:book_locations
end
class Location < Sequel::Model
one_to_many :book_locations
many_to_many :books, :join_table=>:book_locations
# Create a class method to grab the id, and locations from the default
# Location dataset.
def self.all_locations
select(:id, :location).all
end
def purchase(book, copies=1)
bl = book_locations(book)
bl ?
bl.update(:copies=>bl.total+copies) :
BookLocation.create(:book=>book, :location=>self,
:total=>copies, :checked_out=>0)
end
end
class BookLocation < Sequel::Model(:books_locations)
many_to_one :books
many_to_one :locations
end
>>
and here's some test code I wrote:
b = Book.create(:title => 'Snow Crash')
l = Location.create(:location => 'Irvine')
bl = BookLocation.create(:book=>b, :location=>l, :total=>1, :checked_out =>
0)
When I try to add the book location (similar to the purchase() method
above), I get an error:
Sequel::Error: method book= doesn't exist or access is restricted to it.
Thanks again for the help.
Scott
On Sun, Jul 12, 2009 at 10:17 AM, Scott LaBounty <[email protected]>wrote:
> Jeremy,
>
> Thanks I'll mull that over and see what I can do with it. I appreciate all
> the help.
>
> Scott
>
>
> On Sat, Jul 11, 2009 at 10:39 PM, Jeremy Evans <[email protected]>wrote:
>
>>
>> On Jul 11, 7:45 pm, Scott LaBounty <[email protected]> wrote:
>> > OK, I'm getting confused with the foo, bar, baz thing. I'm trying to do
>> > something very similar (in fact I was going to ask before I saw this
>> > thread). I have a library app. with books and locations. Each book can
>> have
>> > many locations and each location can have many books. What I'm trying to
>> add
>> > is a "total" and a "checked_out" value for each book at each location.
>> Based
>> > on the above, what I have for my tables are (from my migration):
>> >
>> >
>> > create_table(:books) do
>> > primary_key :id
>> > String :title
>> > end
>> >
>> > create_table(:locations) do
>> > primary_key :id
>> > String :location
>> > end
>> >
>> > create_table(:books_locations) do
>> > primary_key :id
>> > foreign_key :location_id, :locations
>> > foreign_key :book_id, :books
>> > Integer :total
>> > Integer :checked_out
>> > end
>> >
>> > and my models:
>> >
>> > class Book < Sequel::Model
>> one_to_many :book_locations
>> many_to_many :locations, :join_table=>:book_locations
>> > end
>> >
>> > class Location < Sequel::Model
>> one_to_many :book_locations
>> many_to_many :books, :join_table=>:book_locations
>> > end
>> >
>> class BookLocation < Sequel::Model
>> many_to_one :book
>> many_to_one :location
>> > end
>> >
>> > The BookLocations is what I gather from Jeremy's post that I need
>> (should
>> > those lines be "many_to_many" though?
>> >
>> > Now though, I'm not sure what I need to add to the Book model to let me
>> add
>> > count and checked_out values (and change them) for a given destination.
>> >
>> > Thoughts?
>>
>> The association modification methods are fairly generic, for domain
>> specific behavior like you probably need, you probably should write
>> your own methods that use the BookLocation model. Something like:
>>
>> class Location
>> def purchase(book, copies=1)
>> bl = book_location(book)
>> bl ? bl.update(:copies=>bl.copies+copies) : BookLocation.create
>> (:book=>book, :location=>self, :total=>copies, :checked_out=>0)
>> end
>> def sold(book, copies=1)
>> bl = book_location(book)
>> bl.update(:copies=>bl.copies-copies)
>> end
>> def checkout(book)
>> bl = book_location(book)
>> bl.update(:checked_out=>bl.copies+1)
>> end
>> def checkin(book)
>> bl = book_location(book)
>> bl.update(:checked_out=>bl.copies-1)
>> end
>> def book_location(book)
>> book_locations_dataset[:book_id=>book.id]
>> end
>> end
>>
>> That's just a guess based on the probable needs of your app.
>>
>> Jeremy
>> >>
>>
>
>
> --
> Scott
> http://steamcode.blogspot.com/
>
--
Scott
http://steamcode.blogspot.com/
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