How to check if a record exists before creating a new one in rails3?

Question

Heres what I\'m trying to accomplish:

• I have a tagging system in place.
• Tags are created, when Posts are created (posts has_many :tags, :through => :tag

Answer 1

You're going to find it hard to to this from within the Tag model. It seems like what you want is to update the Post using nested attributes, like so:

post = Post.create
post.update_attributes(:tags_attributes=>{"0"=>{:name=>"fish",:user_id=>"37"}})

This is actually pretty simple to do by using a virtual attribute setter method:

class Post < AR::Base
  has_many :tags

  def tags_attributes=(hash)
    hash.each do |sequence,tag_values|
      tags <<  Tag.find_or_create_by_name_and_user_id(tag_values[:name],\
        tag_values[:user_id])
    end
  end

> post = Post.create
> post.update_attributes(:tags_attributes=>{"0"=>{:name=>"fish",:user_id=>"37"}})
> Tag.count # => 1
# updating again does not add dups
> post.update_attributes(:tags_attributes=>{"0"=>{:name=>"fish",:user_id=>"37"}})
> Tag.count # => 1