How do I get rid of undefined method `to_sym' for nil:NilClass error when deleting rows in rails?

Question

My project is at this github: https://github.com/hoolahoop/RoR_Projects.

I have a project which has Users, Events, and a join table between the two tables. An event is owned by a user, with a foreign key on the event table. The join table allows many users to be guests for many events.

I'm trying to let owners of events add and delete multiple guests at a time. Below is the controller action code that throws the error when deleting rows from the join table. Ctrl + f "error thrown here" to see where the error is thrown.

def create
    Rails.logger.event.debug("===New Create===\n")
    @user_check = true;

    #@event = Event.new(event_params)
    @event = Event.new(event_user_params)

    @users = User.new

    @event.users.each do |user|
        user.password = SecureRandom.base64
        user.password_confirmation = user.password
        #test all saves here
        if(!user.try(:save))
            user_check = false;
        end
    end
    Rails.logger.event.debug("Can we save all users: #{@user_check}. If true, continue.")
    if(@user_check)
        #add all saves here
        #add all associations here
        @event.users.each do |user|
            @user_in_database = User.find_by email: user.email
            Rails.logger.event.debug("User in database check. Id: #{@user_in_database.id}. Email: #{@user_in_database.email}.")
            if (@user_in_database.nil?) # if user is not in the database (unique email check)
                # create a new user
                User.transaction do
                    user.save
                end
                Rails.logger.event.debug("User id check: #{@user}")
                @event_user = EventUser.new(user_id: user.id, event_id: params[:event_id])
                # create a new join table record
                EventUser.transaction do
                    @event_user.save
                end
            else
                @event_user_join = EventUser.find_by user_id: @user_in_database.id, event_id: params[:event_id]
                Rails.logger.event.debug("Is there a join on this event for this user?. Join object: #{@event_user_join}. If this is nil, no join exists.")
                if (@event_user_join.nil?)
                    @event_user = EventUser.new(user_id: @user_in_database.id, event_id: params[:event_id])
                    EventUser.transaction do
                        @event_user.save
                    end
                else
                    Rails.logger.event.debug("Join user_id: #{@event_user_join.user_id}. Join event_id: #{@event_user_join.event_id}.")
                    Rails.logger.event.debug("Try removing join.")
                    EventUser.transaction do
                        @event_user_join.delete
                    end
                    Rails.logger.event.debug("Removal success.")
                end
            end
        end
        Rails.logger.event.debug("===Redirect to Event Guests Page===\n")
        redirect_to event_display_path(params[:event_id])
    else
        render 'new'
        Rails.logger.event.debug("===Render New===\n")
    end
end

private
    def event_user_params
        #params.require(:user).permit(:first_name, :last_name, :email)
        params.require(:event).permit(users_attributes: [:id, :first_name, :last_name, :email, :_destroy])
    end

    def random_password
        random_pass = SecureRandom.base64

    end

Models:

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  has_many :event_users
  has_many :events, through: :event_users
  #validation code...
end

class EventUser < ApplicationRecord
  belongs_to :event
  belongs_to :user
end

class Event < ApplicationRecord
  #belongs_to :user
  belongs_to :owner, class_name: "User", foreign_key: :user_id
  has_many :event_users
  has_many :users, through: :event_users

  accepts_nested_attributes_for :users
  #validation code...
end

Migrations:

class DeviseCreateUsers < ActiveRecord::Migration[5.1]
  def change
    create_table :users do |t|
      ## Database authenticatable
      t.string :email,              null: false, default: ""
      t.string :encrypted_password, null: false, default: ""

      ## Recoverable
      t.string   :reset_password_token
      t.datetime :reset_password_sent_at

      ## Rememberable
      t.datetime :remember_created_at

      ## Trackable
      t.integer  :sign_in_count, default: 0, null: false
      t.datetime :current_sign_in_at
      t.datetime :last_sign_in_at
      t.string   :current_sign_in_ip
      t.string   :last_sign_in_ip

      t.timestamps null: false
    end

    add_index :users, :email,                unique: true
    add_index :users, :reset_password_token, unique: true
  end
end

class AddNamesToUsers < ActiveRecord::Migration[5.1]
  def change
    add_column :users, :first_name, :string, null: false, default: ""
    add_column :users, :last_name, :string, null: false, default: ""
  end
end

class CreateEvents < ActiveRecord::Migration[5.1]
  def change
    create_table :events do |t|
      t.string :name,              null: false, default: ""
      t.text :description,         null: true
      t.integer :option,           null: false, default: 1
      t.string :street_address,    null: true
      t.integer :apartment_number, null: true
      t.string :city,              null: true
      t.date :date,                null: true
      t.time :time,                null: true
      t.string :password,          null: false, default: ""
      t.references :user, foreign_key: true
    end
  end
end

class CreateJoinTableEventUser < ActiveRecord::Migration[5.1]
  def change
    create_join_table :events, :users do |t|
      t.index [:event_id, :user_id]
      t.index [:user_id, :event_id]
    end
  end
end

class RenameTableEventsUsers < ActiveRecord::Migration[5.1]
  def change
    rename_table :events_users, :event_users
  end
end

Full error in command prompt:

app/controllers/users_controller.rb:21:in `create'
Started POST "/events/16/users" for 127.0.0.1 at 2018-03-05 10:06:40 -0500
Processing by UsersController#create as HTML
Parameters: {"utf8"=>"√", "authenticity_token"=>"ph5zsZQ0HhHt2NAsCtGFDUo/+PmlrQmKyeXt6dcQMnnXFVoEgeh4Srp+p0z0C8mtOhF6Uf48suCw+2YO72+bzw==", "event"=

{"users_attributes"=>{"0"=>{"first_name"=>"Test1", "last_name"=>"Test11", "email"=>"test1@test.com", "_destroy"=>"false", "id"=>"8"}, "1"=>{"first_na me"=>"Test4", "last_name"=>"Test44", "email"=>"test4@test.com", "_destroy"=>"false", "id"=>"11"}, "2"=>{"first_name"=>"Test5", "last_name"=>"Test55", "email"=>"test5@test.com", "_destroy"=>"false", "id"=>"12"}}}, "commit"=>"Save", "event_id"=>"16"}

Unpermitted parameter: :id
Unpermitted parameter: :id
Unpermitted parameter: :id

(0.0ms) begin transaction User Exists (0.0ms) SELECT 1 AS one FROM "users" WHERE "users"."email" = ? LIMIT ? [["email", "test1@test.com"], ["LIMIT", 1]]
(0.0ms) rollback transaction
(0.0ms) begin transaction User Exists (0.0ms) SELECT 1 AS one FROM "users" WHERE "users"."email" = ? LIMIT ? [["email", "test4@test.com"], ["LIMIT", 1]]
(0.0ms) rollback transaction
(0.0ms) begin transaction User Exists (0.0ms) SELECT 1 AS one FROM "users" WHERE "users"."email" = ? LIMIT ? [["email", "test5@test.com"], ["LIMIT", 1]]
(0.0ms) rollback transaction
User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."email" = ? LIMIT ? [["email", "test1@test.com"], ["LIMIT", 1]]
EventUser Load (0.0ms) SELECT "event_users".* FROM "event_users" WHERE "event_users"."user_id" = ? AND "event_users"."event_id" = ? LIMIT ? [["us er_id", 8], ["event_id", 16], ["LIMIT", 1]]
(0.0ms) begin transaction
(0.0ms) rollback transaction
Completed 401 Unauthorized in 441ms (ActiveRecord: 2.0ms)

NoMethodError (undefined method `to_sym' for nil:NilClass):

app/controllers/users_controller.rb:56:in block (2 levels) in create' app/controllers/users_controller.rb:54:inblock in create' app/controllers/users_controller.rb:34:in `create'

Full error on browser

NoMethodError in UsersController#create undefined method `to_sym' for nil:NilClass Extracted source (around line #65): 63 64 65 66 67 68

                    Rails.logger.event.debug("Try removing join.")
                    EventUser.transaction do
                        @event_user_join.delete
                    end
                    Rails.logger.event.debug("Removal success.")
                end

Rails.root: D:/Development/RoR_Projects/Maestro/blog

Application Trace | Framework Trace | Full Trace app/controllers/users_controller.rb:65:in block (2 levels) in create' app/controllers/users_controller.rb:64:inblock in create' app/controllers/users_controller.rb:39:in `create' Request Parameters:

{"utf8"=>"✓","authenticity_token"=>"HfCo+U+X7DtWUrCn/O2KFEkioGtXyut99NEsjUL08DBs+4FMWkuKYAH0x8cCN8a0OQwiwwxbUBeNz6dqeotZhg==",
"event"=>
{"id"=>"16",
"owner"=>"5",
"users_attributes"=>
{"0"=>{"first_name"=>"Test1", "last_name"=>"Test11", "email"=>"test1@test.com", "_destroy"=>"false", "id"=>"8"},
 "1"=>{"first_name"=>"Test4", "last_name"=>"Test44", "email"=>"test4@test.com", "_destroy"=>"false", "id"=>"11"},
 "2"=>{"first_name"=>"Test5", "last_name"=>"Test55", "email"=>"test5@test.com", "_destroy"=>"false", "id"=>"12"}}},
"commit"=>"Save",
"event_id"=>"16"}

Version information:

OS: Windows 7 Professional Service Pack 1

Ruby -v: ruby 2.4.3p205 (2017-12-14 revision 61247) [x64-mingw32]

Rails -v: Rails 5.1.4

Libraries: please check gemfile.

Related lib's to this problem include gem 'bcrypt', '~> 3.1.11', gem 'devise', and gem 'cocoon'.

Additional Information:

If you need any more information to help debug this problem, I will be happy to edit this post.

I don't know where the to_sys no method error is coming from. I've found a few places inside devise where it is used, but I'm having trouble deciphering why it's happening, and which exact place it's being used.

I'm using cocoon to generate multiple user fields on my form, and then trying to save them all. Perhaps I'm using cocoon incorrectly. The sample projects didn't seem to cover my use case of having a join table.

Devise github: https://github.com/plataformatec/devise Cocoon github: https://github.com/nathanvda/cocoon