Sequel accessing many_to_many join table when adding association - ruby

Question

I'm building a wishlist system using Sequel. I have a wishlists and items table and an items_wishlists join table (that name is what sequel chose). The items_wishlists table also has an extra column for a facebook id (so I can store opengraph actions), which is a NOT NULL column.
I also have Wishlist and Item models with the sequel many_to_many association set up. The Wishlist class also has the :select option of the many_to_many association set to select: [:items.*, :items_wishlists__facebook_action_id].
Is there a way that I can add in extra data when creating the association, like wishlist.add_item my_item, facebook_action_id: 'xxxx' or something? I can't do it after I create the association as the facebook id is has NOT NULL on the column.
Thanks for any help

Answer 1

The recommended way to do this is to add a model for the join table. However, if you don't want to do that, you can do:
class Wishlist
def _add_item(item, hash={})
model.db[:items_wishlists].insert(hash.merge(:item_id=>item.id, :wishlist_id=>id))
end
end

Answer 2

I think there is also another possibility.
First a MWE (minimal working example) of your question:
require 'sequel'
Sequel.extension :pretty_table #Sequel::PrettyTable.print()/Sequel::PrettyTable.string()
DB = Sequel.sqlite
DB.create_table(:wishlists){
primary_key :id
String :listname
}
DB.create_table(:items){
primary_key :id
String :descr
}
DB.create_table(:items_wishlists){
primary_key :id
foreign_key :wishlist_id, :wishlists
foreign_key :item_id, :items
add_column :facebook_id, type: :nvarchar
}
class Item < Sequel::Model
many_to_many :wishlists
end
class Wishlist < Sequel::Model
many_to_many :items
end
w1 = Wishlist.create(listname: 'list1')
w1.add_item(Item.create(descr: 'item 1'))
#w1.add_item(Item.create(descr: 'item 2'), facebook_id: 'fb2') ##<- This does not work
#Sequel::PrettyTable.print(Wishlist)
#Sequel::PrettyTable.print(Item)
Sequel::PrettyTable.print(DB[:items_wishlists])
To allow ad_itemwith a parameter (Wishlist#add_item(Item.create(descr: 'item 2'), facebook_id: 'fb2')) you must define an adder as in this example:
require 'sequel'
Sequel.extension :pretty_table
Sequel::PrettyTable.print()/Sequel::PrettyTable.string()
DB = Sequel.sqlite
DB.create_table(:wishlists){
primary_key :id
String :listname
}
DB.create_table(:items){
primary_key :id
String :descr
}
DB.create_table(:items_wishlists){
primary_key :id
foreign_key :wishlist_id, :wishlists
foreign_key :item_id, :items
add_column :facebook_id, type: :nvarchar
}
class Item < Sequel::Model
#~ many_to_many :wishlists
end
class Wishlist < Sequel::Model
many_to_many :items,
join_table: :items_wishlists, class: Item,
left_key: :wishlist_id, right_key: :item_id,
adder: (lambda do |item, facebook_id: nil|
self.db[:items_wishlists].insert(wishlist_id: self.id, item_id: item.id, facebook_id: facebook_id)
end)
end
w1 = Wishlist.create(listname: 'list1')
w1.add_item(Item.create(descr: 'item 1'))
w1.add_item(Item.create(descr: 'item 2'), facebook_id: 'fb2')
Sequel::PrettyTable.print(DB[:items_wishlists])
The result:
+-----------+--+-------+-----------+
|facebook_id|id|item_id|wishlist_id|
+-----------+--+-------+-----------+
| | 1| 1| 1|
|fb2 | 2| 2| 1|
+-----------+--+-------+-----------+
But the next problem will come later:
With w1.items you get the list of items, but you have no access to the parameters. (at least I found no way up to now. I'm still researching, but I expect, that I need a model of the join table for this (see Jeremys recommendation))