Question

Let’s say I have a has_many relation between User and Messages.

I’d like to set a scope to be able to filter users by the ones who have something in the last message they posted. So searching only among each user’s last message.

Below I got the results among all messages…

class Contact < ActiveRecord::Base
    has_many :messages

    scope :filter_by_last_messages, lambda { |value|
        joins(:messages).where("messages.content = ?", value)
    }
end

Answer 1

I figured it out by creating a belongs_to relation with the last message, in my User class.

belongs_to :last_message, :class_name => 'Message'

I set my last message in an after_create in Message class.
Then my scope is simply as follow:

scope :filter_by_last_messages, lambda { |value|
    joins(:last_message).where("content = ?", value)
}