Has_many association with two foreign keys

Rails
1

Hello,

I was wondering if there is a way to specify two foreign keys on a
has_many association. I have a conversation model with a sender_id and
recipient_id. A user can be the sender or recipient of a conversation.
To fetch all conversations I must specify the sender_id and
recipient_id on the User model, but I can only specify one of the two
as shown below.

class User < ActiveRecord::Base
has_many :conversations, :foreign_key => ‘sender_id’
end

Is there any way to specify two foreign keys?

Thanks!

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2

I don’t think there is…

but if you need to encompass that in a single AR association, you
could changed the table design to:

Users

UserConversations
user_id
conversation_id
participation_type

Conversations

then you could have several different through associations from user
to conversation, with or without participation_type.

On Dec 22, 3:22 am, elioncho [email protected] wrote:

has_many :conversations, :foreign_key => ‘sender_id’
end

Is there any way to specify two foreign keys?

Thanks!

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3

JDevine wrote:

I don’t think there is…

but if you need to encompass that in a single AR association, you
could changed the table design to:

Users

UserConversations

That should be called Participations or something.

user_id
conversation_id
participation_type

Conversations

then you could have several different through associations from user
to conversation, with or without participation_type.

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

4

Elias O. wrote:

Hello,

I was wondering if there is a way to specify two foreign keys on a
has_many association. I have a conversation model with a sender_id and
recipient_id. A user can be the sender or recipient of a conversation.
To fetch all conversations I must specify the sender_id and
recipient_id on the User model, but I can only specify one of the two
as shown below.

class User < ActiveRecord::Base
has_many :conversations, :foreign_key => ‘sender_id’
end

Is there any way to specify two foreign keys?

Sure! You can have two separate associations between the same tables –
or follow JDevine’s suggestion.

Thanks!

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Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]

5

another cool way would be to say

has_many :conversations, :foreign_key => ‘sender_id’, :conditions =>
‘recipient_id = #{id}’

make sure to use single quotes here, or it won’t evaluate the #{}

On Tue, Dec 22, 2009 at 9:13 AM, Marnen Laibow-Koser
[email protected]wrote:

class User < ActiveRecord::Base

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