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

Extract the tag name for security. Check whether or not the tag exists in your tags table, then create it if it doesn't:

name = params[:tag][:name]
@new_tag = Tag.where(name: name).first_or_create

Then check whether it exists within this specific collection, and push it if it doesn't:

@taggable.tags << @new_tag unless @taggable.tags.exists?(@new_tag)