我猜你正在使用 Rails 4.如果是这样，必须将所需的参数标记为必需.

I guess you are using Rails 4. If so, the needed parameters must be marked as required.

你可能想这样做:

class UsersController < ApplicationController

  def create
    @user = User.new(user_params)
    # ...
  end

  private

  def user_params
    params.require(:user).permit(:username, :email, :password, :salt, :encrypted_password)
  end
end