has_and_belongs_to_many, avoiding dupes in the join table

Question

I have a pretty simple HABTM set of models

class Tag < ActiveRecord::Base 
   has_and_belongs_to_many :posts
end 

class Post < ActiveRecord::Base 
           


        

Answer 1

Just add a check in your controller before adding the record. If it does, do nothing, if it doesn't, add a new one:

u = current_user
a = @article
if u.articles.exists?(a)

else
  u.articles << a
end

More: "4.4.1.14 collection.exists?(...)" http://edgeguides.rubyonrails.org/association_basics.html#scopes-for-has-and-belongs-to-many