I’m stumped on this one and after lots of searching and reading I need
some help, please!
I’m trying to model a “purchase” as occurring between a “seller” and a
“buyer”, both of which are instances of a User class.
I have:
class User < ActiveRecord::Base
has_many :purchases, :as => :seller, :dependent => true
has_many :purchases, :as => :buyer, :dependent => true
…
end
class Purchase < ActiveRecord::Base
belongs_to :seller, :class_name => “User”, :foreign_key =>
“seller_id”
belongs_to :buyer, :class_name => “User”, :foreign_key => “buyer_id”
…
end
The users table doesn’t define any keys, but the purchases table is:
create_table “purchases” do |t|
t.column :seller_id, :integer, :null => false
t.column :buyer_id, :integer, :null => false
… (other columns)
end
The problem is that this isn’t working as expected. I tried some
polymorphic options, but I don’t think that’s what’s needed (although
I’m not sure, honestly). Do I need to change the model associations?
And if so, how? I know with polymorphic associations, I would set a
“seller_type” and “buyer_type” on the purchases table, but it’s not
polymorphic, is it?
This seems to me to be an easy and common thing, but I’ve been stumped
for a while (I’m not a Rails newbie, but I’ve cough, cough not been
keeping up with it, so I’m trying to learn all the new stuff since
Rails 1.0. DOH!)
Thanks for the attempt. It didn’t work, though. Unless I have the
“purchases” class set wrong. If I manually create a record in the DB,
with two users and one purchase, one as the seller and one as the
buyer… and then do:
User.find(1).sales
or
User.find(1).purchases
I get an error that it is looking for "purchases.seller_type or
purchases.buyer_type. But if they are both “User”, can’t that be set
somewhere rather than having seller_type and buyer_type fields on the
purchases table?
Actually, I tried setting the seller_type and buyer_type fields on the
purchases table and it sort-of works. If I manually create a purchase
entry and populate the fields in the DB record, and put “User” for the
type fields, then it works. But, if I create a new purchase and give
it two users, it creates the record but puts “NULL” in the purchases
table for the seller_type and buyer_type. How would these get set to
“User”? Or does that need to happen manually?
I’m stumped on this one and after lots of searching and reading I need
some help, please!
I’m trying to model a “purchase” as occurring between a “seller” and a
“buyer”, both of which are instances of a User class.
I have:
class User < ActiveRecord::Base
has_many :purchases, :as => :seller, :dependent => true
has_many :purchases, :as => :buyer, :dependent => true
…
end
class Purchase < ActiveRecord::Base
belongs_to :seller, :class_name => “User”, :foreign_key =>
“seller_id”
belongs_to :buyer, :class_name => “User”, :foreign_key => “buyer_id”
…
end
The users table doesn’t define any keys, but the purchases table is:
create_table “purchases” do |t|
t.column :seller_id, :integer, :null => false
t.column :buyer_id, :integer, :null => false
… (other columns)
end
The problem is that this isn’t working as expected. I tried some
polymorphic options, but I don’t think that’s what’s needed (although
I’m not sure, honestly). Do I need to change the model associations?
And if so, how? I know with polymorphic associations, I would set a
“seller_type” and “buyer_type” on the purchases table, but it’s not
polymorphic, is it?
Also, I realized I need some way to figure out for a given user what
purchases they had (a) in general, (b) as a seller and (c) as a buyer.
Assuming the associations are correct, I can do (a) via:
User.find(1).purchases, but how would I do (b) or (c)?
This seems to me to be an easy and common thing, but I’ve been stumped
for a while (I’m not a Rails newbie, but I’ve cough, cough not been
keeping up with it, so I’m trying to learn all the new stuff since
Rails 1.0. DOH!)
Josh, I’ve read your stuff a TON! (It’s really helped me catch up with
Rails) I can’t believe I didn’t think of that very post. I’m gonna go
refactor the code that way as it looks like exactly what I need.
