Multiple foreignkeys for same model with different meaning (User.received_messages / User.sent_messages/ -> User.messages?)

rubyonrails-talk
1

Hello,

I have 2 models: User and Message

Message: belongs_to :sender, :class_name=>'User', :foreign_key=>'sender_id' belongs_to :receiver, :class_name=>'User', :foreign_key=>'receiver_id'

// MESSAGE-MIGRATION START create_table :messages do |t|       t.integer :sender_id       t.integer :receiver_id       t.string :subject       t.text :content

      t.timestamps     end // MIGRATION END

User:   has_many :sent_messages, :class_name => "Message", :foreign_key => "sender_id"   has_many :received_messages, :class_name => "Message", :foreign_key => "receiver_id"

I want to access User.messages, because I need it for the destroy- action -> User.messages.find(params[:id])

Can anyone help me? Thanks!

2

Hmmm...

It worked with:

has_many :friendships, :class_name => "Friendship", :foreign_key => "sender_id = #{self.id} or friendships.receiver_id = #{self.id} AND 1"

But thats not very nice...!!??!!?! Is there a better solution??

3

I want to access User.messages, because I need it for the destroy- action -> User.messages.find(params[:id])

You want a single association that covers both sent and received messages ? AFAIL there is no way to get an association to do that (although you could construct a named scope that did).

Fred

4

Hm, I tried it with named scopes, but

User.rb:

named_scope :messages, :join => :messages, :conditions = ["sender_id = ? or receiver_id = ?", self.id, self.id]

returns the collection of USERS -> not messages!

Or is there chance to get the messages?

5

You'd have to put the scope on Message class if you want it to return messages ie named_scope :for_user, lambda {|u| :conditions => ["sender_id = ? or received_id = ?", u,u]}

Then Message.for_user(bob) returns a scope for bob's messages. You could define a messages method on user to make this flow slightly nicer ie

def messages   Message.for_user(self) end

Fred

6

Cool, thx!

Nice idea...