如何验证不与db列对应的参数？

Question

I have a model User with a string attribute name . On my form to create a new User , it's easy to validate the name attribute:

models/user.rb

validates :name, presence: true, length: {maximum: 13}

users_controller.rb

private

def user_params
  params.require(:user).permit(:name, :words)
end

However, I want to validate a param that isn't an attribute or db column. On my form I have a textbox that submits params["words"] as a string. I know the param is being submitted because I can interact with it using binding.pry . But if I try to validate it the same way as Name, nothing happens. The form submits with or without words . How can I validate a param that isn't an attribute?

my form:

<%= form_for @user, :url => users_path do |f| %>
  <%= f.text_field :name %>
  <input id="words" name="words">
  <%= f.submit "Submit", class: "btn" %>
<% end %>

Answer 1

If you want to perform model validations that include :words then you need to add :words as a virtual attribute in your User.rb file so the model has access to it. You can do that simply by adding this line to your User.rb file:

attr_accessor :words

Then your model can now perform validations on it such as:

validates_presence_of :words

You also need to ensure that the :words param belongs to :user and is being sent as params["user"]["words"]

---

Edit:

To get your form to post the :words parameter nested under :user change your form input to:

<input id="words" name="user[words]">

or since the user model now has the virtual attribute :words you can set your form the rails way.

<%= f.text_field :words %>

---

APIDock reference on attr_accessors: http://apidock.com/ruby/Module/attr_accessor

Virtual Attribute Reference: http://www.linuxtopia.org/online_books/programming_books/ruby_tutorial/Ruby_Classes_Objects_and_Variables_Virtual_Attributes.html

Answer 2

该表单应提交params['user']['words']而不是params['words'] ，并且您的User模型应具有attr_accessor :words 。

Answer 3

尝试将您的值放在params[:user][:words]而不是params[:words]然后在模型中添加attr_accessor :words 。

Answer 4

You can do it adding the words attribute to User class.

class User < ActiveRecord::Base
  attr_accessor :words

  validates :words, presence: true, length: {maximum: 13}

  def initialize(arguments = {}, options = {})
    self.words = arguments.delete :words
    super
  end
end

But, override ActiveRecord initialize method isn't recommended. It seems that this validation should occurs only in this action.

The correct approach should be use a Form Object. You can learn more here: http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/