I'm not sure I understand the use of this method def all. If you're trying to grab the first_name of your promoter you should only need promoter_instance.user.first_name.

All logic with params should be handled in your controllers venue_params.

I like what this validation is doing, but your logic can be simplified. First, because of your associations you don't need to call venue = Venue.find(self.venue_id) self.venue is already that venue. Think about how your conditionals are working and what your end goal is. If your time_slot is filled then you can add the error inside of your conditional instead of using the available variable.

Whenever you're doing multiple of the same .find in your controller you should move that logic into a private helper method. For example in your ApplicationController you are calling @user = User.find(session[:user_id]) a few times. What you could do is:

class ApplicationController < ActionController::Base
  before_action :set_user, only: [:action1, :action2]

  ...

  private

  def set_user
    @user = User.find(session[:user_id])
  end
end

Because you're not referencing the password_exists private method in your UsersController more than once I would not turn that logic into it's own method.

Try to handle most of your view logic in your models. For example your time_slot_applications/index.html.erb has way too much logic and data manipulation. I would turn your strftime() calls into helper functions and the calls to a users's full_name into a method in the time_slot_application class.

Overall, this application turned out really well! You should all be very proud of yourselves. Everything from the domain modeling to the logic has complex functionality. @aemrich @cy2003 @robhitt @ValerieMcCarthy