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问题:

I am working on the rails tutorial book online and I am getting the following error message when I go to http://localhost:3000/

"uninitialized constant ApplicationRecord"

and it gives me the following code highlighting the first line.

class User < ApplicationRecord   attr_accessor :remember_token   before_save { self.email = email.downcase }   validates :name,  presence: true, length: { maximum: 50 }   VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i   validates :email, presence: true, length: { maximum: 255 },

Here is my application.html.erb file:

<!DOCTYPE html> <html>   <head>     <title><%= full_title(yield(:title)) %></title>     <%= stylesheet_link_tag "application", media: "all",                                            "data-turbolinks-track" => true %>     <%= javascript_include_tag "application", "data-turbolinks-track" => true %>     <%= csrf_meta_tags %>     <%= render 'layouts/shim' %>   </head>   <body>     <%= render 'layouts/header' %>     <div class="container">       <% flash.each do |message_type, message| %>         <div class="alert alert-<%= message_type %>"><%= message %></div>       <% end %>       <%= yield %>       <%= render 'layouts/footer' %>       <%= debug(params) if Rails.env.development? %>     </div>   </body> </html>

And my user.rb file :

class User < ApplicationRecord   attr_accessor :remember_token   before_save { self.email = email.downcase }   validates :name,  presence: true, length: { maximum: 50 }   VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i   validates :email, presence: true, length: { maximum: 255 },                     format: { with: VALID_EMAIL_REGEX },                     uniqueness: { case_sensitive: false }   has_secure_password   validates :password, presence: true, length: { minimum: 6 }    # Returns the hash digest of the given string.   def User.digest(string)     cost = ActiveModel::SecurePassword.min_cost ? BCrypt::Engine::MIN_COST :                                                   BCrypt::Engine.cost     BCrypt::Password.create(string, cost: cost)   end    # Returns a random token.   def User.new_token     SecureRandom.urlsafe_base64   end    # Remembers a user in the database for use in persistent sessions.   def remember     self.remember_token = User.new_token     update_attribute(:remember_digest, User.digest(remember_token))   end    # Returns true if the given token matches the digest.   def authenticated?(remember_token)     return false if remember_digest.nil?     BCrypt::Password.new(remember_digest).is_password?(remember_token)   end    # Forgets a user.   def forget     update_attribute(:remember_digest, nil)   end end

回答1:

It appears you're using the Rails 5 tutorial, but working with Rails 4. In Rails 5 all models inherit from ApplicationRecord, while Rails 4 from ActiveRecord::Base

Immediate fix:

class User < ActiveRecord::Base ... end

Long term fix, switch to Rails 5 and learn with Rails 5

回答2:

Referring to infused's answer from https://stackoverflow.com/a/41388844/5598043

Create a new file called app/models/application_record.rb with the following contents:

class ApplicationRecord < ActiveRecord::Base self.abstract_class = true end

文章来源: uninitialized constant ApplicationRecord

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