Validate uniqueness of many to many association in Rails

Question

Say I have Project, that is in many-to-many association with Tag. I\'m using has_many through so I have separate join model.

H

Answer 1

Try validates_associated.

That should, I believe, allow the join model validations to run before saving. So in your case:

class Project
   has many :tags, :through => :taggings
   validates_associated :taggings
end

class Taggings
   belongs_to :tags

   #your validations here....
end

class Tag
   has_many :taggings
end