如何使这项工作成为一个has_many：通过

Question

I'm wondering if you can give me some advice on how to use a has_many :through association in this situation before I spend a whole lot of time rewriting my code to possibly no avail.

I have a user model, and each user can play many quizzes (and therefore generate many quiz scores). Right now, the player starts a game by clicking on a user's name, which triggers a query for all the quiz questions that that user (a user has_many :questions) has made

  def startGame 

     user = User.find_by_name(params[:user])
     questions = user.questions

  end 

For obvious reasons, a player can't play the same quiz twice. Although I figured out a way to prevent that, I didn't do it an efficient way. Someone suggested I try an association table. I started that association table as a has_many :through with this plan

User.rb (this user is the user-as-player, not the user-as-quiz maker)

has_many :scores
has_many :quizzes, :through => :scores

Quiz.rb

   has_many :scores
   has_many :users    :through => :scores

Score

   belongs_to :user
   belongs_to :quiz

The problem is that, currently, there is no quiz model or quiz anything. Quizzes are in fact just made up of questions (Question.rb) and answers (Answer.rb). For example, each user has_many :questions and each question has_many :answers like this

User.rb

has_many :questions

Question.rb

has_many :answers

So what can I make the Quiz model (or whatever I would call it) out of?

One idea that occured to me was to make a Quiz.rb model and do

has_many :questions

which would mean Question.rb belongs to both User.rb and Quiz.rb.

Can I then do the has_many :through as described above with User, Quiz and Score? If so, Score will have both a user_id (for the player) and a quiz_id (for the quiz), but since the purpose of this whole association is to prevent users playing the same quiz twice, I'm wondering how I could make it work with the following code.

  def startGame

   user = User.find_by_name(params[:user])  #this user is the quiz creator
   questions = user.questions
     .....
    #I want to check right here if they've already played the quiz. how to do it with the has_many :through of Quiz, Score, User (as player)

  end

With the user.rb (player), score.rb, quiz.rb set up, how would I check if they've played this particular quiz in this situation.

Also, if I make the quiz model and do has_many :questions, would I would have to use polymorphism since user.rb also has_many :questions?

Update: I want to check whether they've already played in the def startGame method and not let them continue the game if they have. ie I don't want to wait until it's time to save the score to see if a score for that quiz has already been saved.

Answer 1

Your code looks very good already. If you want to prevent any player from playing a quiz more than once, you can make any combination of a user and a quiz unique. You can add this to your scores migration:

add_index :scores, [:user_id, :quiz_id], unique: true

And add this to your Scores model:

validates_uniqueness_of :user_id, scope: quiz_id