Username can't be blank - ruby-on-rails

Question

So I enter a username, email, and password (+password confirmation) and it once I hit submit, it says: "Username can't be blank" and I clearly entered a username.
Here is my user.rb
class User < ActiveRecord::Base
validates :user_name, presence: true, length: { minimum: 4, maximum: 16
}
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
end
This is my registrations_controller:
class RegistrationsController < Devise::RegistrationsController
private
def sign_up_params
params.require(:user).permit(:email, :user_name, :password, :password_confirmation)
end
def account_update_params
params.require(:user).permit(:email, :user_name, :password, :password_confirmation, :current_password)
end
end
And the following is my new.html.erb
<h2>Sign up</h2>
<%= simple_form_for(resource, as: resource_name, url: registration_path(resource_name)) do |f| %>
<%= f.error_notification %>
<div class="form-inputs">
<%= f.input :user_name %>
<%= f.input :email, required: true, autofocus: true %>
<%= f.input :password, required: true, hint: ("#{#minimum_password_length} characters minimum" if #minimum_password_length) %>
<%= f.input :password_confirmation, required: true %>
</div>
<div class="form-actions">
<%= f.button :submit, "Sign up" %>
</div>
<% end %>
<%= render "devise/shared/links" %>
add_username_to_users.rb (migration)
class AddUsernameToUsers < ActiveRecord::Migration
def change
add_column :users, :username, :string
add_index :users, :username, unique: true
end
end
If there's any other needed to be posted, to find more about the error, please comment. Also, note that I have devise gem (properly installed) and I'm using a cloud 9 editor. Thanks in advance!

Answer 1

When reviewing your code on c9.io there is definitely an issue with your migrations file where you have this:
class CreateAddUserNameToUsers < ActiveRecord::Migration
def change
create_table :add_user_name_to_users do |t|
t.string :user_name
t.timestamps null: false
end
end
end
That actually created a table called add_user_name_to_users, which you can find in your schema.rb file. So when you are creating your User with the sign up form, there is no user_name to validate on the User's table since it does not exist. You should remove your migration file 20171231162016_create_add_user_name_to_users.rb since it is not what you are looking to do or drop the table (here are some docs for changing your migrations).
Instead make sure you follow this devise documentation on adding a user_name as a sign up/ sign in parameter here.
You also have a models table that has the same fields as your users table (also assuming that this was put here by accident. Make sure you double check your migrations as it looks like that was one of the results of the error you are seeing.