JS事件触发状态机中的后端状态更改（导轨）？

Question

I am working on a new project: the backend has Users which has_many "Courses" which also has_many "Steps".

I want javascript to validate the user's answer - ie let's say the user enters "6", which is the right answer. I would imagine the function to check would look something like this.

function match_answer(course, answer){
}

If the JS event proves true I would like it to change the state_machine on the backend. The state_machine is as follows:

class Step < ActiveRecord::Base
...

  state_machine initial: :pending do
    state :pending, value: 0
    state :finished, value: 1

    event :finish do
      transition :pending => :finished
    end

    event :restart do
      transition :finished => :pending
    end
  end
end

The reason why I want a javascript event to change the state of a state machine is because when the user logs back on I would like them to go the appropriate place in the course.

1) How do I change the state of the state_machine with a javascript event? More specifically, if match_answer function proves true, how do I change the state from :pending to :finished.

2) Assuming the correct answer(which will check against the user's answer) is stored in the database, how do I go about getting the correct answer from the database in order to implement it in the match_answer javascript function to check against the user's answer?

Any help or resources you can point me to would be very much appreciated.

Answer 1

1) In your match_answer javascript function, use an AJAX post to your server application to update what step they're on.

2) In your javascript, you'll need to know the right answer, or possibly a list of questions and correct answers. One way to get this information would be to use the gon gem, which basically lets you set data in your controller just like an @instance variable, only it's made available in your javascript. A drawback would be that the answers would be visible if a user ever did a View Source on the page and looked hard enough. Another way would be to fetch them separately from the server via an AJAX get request, but again the user might be able to snoop the traffic and find them, if that seems at all likely.

Maybe a better approach, since you're going to hit the server anyway for each answer, would be to use AJAX to post the user's answer to the server. If it's right, the server can update the step the user is on and return a 200 status code. If it's a wrong answer, the server can return a 422 status code. Your ajax can use the success callback or the error callback from the ajax request to respond appropriately.