include BCrypt

  #requires username column on Users table
  def self.authenticate(username, password)
    user = User.find_by(username: username)
    if user
      return user if user.password == password
    end
  end

  def password
    @password ||= Password.new(password_hash)
  end

  #requires password_hash column on Users table
  def password=(new_password)
    @password = Password.create(new_password)
    self.password_hash = @password
  end