Could I add an association based on another association?

Question

My User model looks like:

User
   habtm  :Roles


Role
   habtm  :Users


RoleExtension
   belongs_to  :Role

mysql tables:

Answer 1

Try this -

# Fetch user object
user = User.first

# If you want roles of that user try this
roles = user.roles

# You can map all the role extensions of that user by
role_extensions = user.roles.map(&:role_extensions).uniq

Be aware that this will be extremely slow for large number of roles. In that case better write your own query method. Something like

role_extensions = RoleExtension.where("role_id in (?)", user.role_ids).all