.rb

### author.rb

class Author < ApplicationRecord
  has_many :books
  validates :name, presence: true
end


### authors_controllers.rb

class AuthorsController < ApplicationController
  before_action :set_author

  def new
  end

  def create
    if @author.save
      redirect_to root_path
    else
      render 'new'
    end
  end

  private

    def author_params
      params.require(:author).permit(:name, :nationality)
    end
    
    def set_author
      @author = Author.new
    end
end


### authors/new.html.haml

%h2 Add New Author
= render 'form'

### authors/_form.html.haml

= simple_form_for @author do |f|
  = f.input :name, label: 'Author Name'
  = f.input :nationality, label: 'Country'
  = f.button :submit