Rails create and update array in database - mysql

Question

So I have a service object that submits up votes and voted users into a database:
Here's the posts model:
class Post < ActiveRecord::Base
attr_accessible :comment_count, :downvote, :id, :text, :title, :upvote, :url, :user_id, :users_voted_up_by, :users_voted_down_by
serialize :users_voted_up_by, Array
serialize :users_voted_down_by, Array
belongs_to :user
end
Here's the User model:
class User < ActiveRecord::Base
attr_accessible :email, :password, :password_confirmation, :username, :good_karma, :bad_karma, :posts_voted_up_on, :posts_voted_down_on
serialize :posts_voted_up_on, Array
serialize :posts_voted_down_on, Array
has_many :posts
attr_accessor :password
before_save :encrypt_password
validates_confirmation_of :password
validates_presence_of :password, :on => :create
validates_presence_of :email
validates_uniqueness_of :email
validates_presence_of :username
validates_uniqueness_of :username
def self.authenticate(email, password)
user = find_by_email(email)
if user && user.password_hash == BCrypt::Engine.hash_secret(password, user.password_salt)
user
else
nil
end
end
def encrypt_password
if password.present?
self.password_salt = BCrypt::Engine.generate_salt
self.password_hash = BCrypt::Engine.hash_secret(password, password_salt)
end
end
end
Now here's my Voter class that controls up votes and down votes.
class Voter
def initialize(post, user)
#post = post
#user = user
end
def upvote
return false unless #post.users_voted_up_by
#post.upvote += 1
#post.users_voted_up_by << #user.username
#user.good_karma += 1
#post.save && #user.save
end
def downvote
return false unless #post.users_voted_down_by
#post.upvote += 1
#post.users_voted_down_by << #user.username
#user.bad_karma += 1
#post.save && #user.save
end
end
It adds and retrevies the first one fine:
User1
But when I perform another "upvote" with a different user, instead of adding it to the array it just adds it to the string like this:
User1User2
Am I not using the line correctly?
#post.users_voted_up_by << #user.username

Answer 1

You're trying to model a many-to-many relationship via serialized arrays. In my opinion this is a misuse of Rails serialization feature.
The more appropriate way to design your problem is to create a Vote model which belongs to User and has one Post. It is better both in design perspective and db-performance perspective.
Once you do that you won't add users to a post votes array, you will just create a new Vote instance with the voter (user) id and the post id.