未初始化的常量 ApplicationRecord
uninitialized constant ApplicationRecord
我正在在线编写 rails 教程书,当我转到 http://localhost:3000/
时收到以下错误消息
"uninitialized constant ApplicationRecord"
它给了我以下突出显示第一行的代码。
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 },
这是我的 application.html.erb 文件:
<!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>
还有我的 user.rb 文件:
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
看来您使用的是 Rails 5 教程,但使用的是 Rails 4。在 Rails 5 中,所有模型都继承自 ApplicationRecord
,而 Rails 4 来自 ActiveRecord::Base
立即修复:
class User < ActiveRecord::Base
...
end
长期修复,切换到 Rails 5 并学习 Rails 5
参考
中 infused 的回答
创建一个名为 app/models/application_record.rb
的新文件,内容如下:
class ApplicationRecord < ActiveRecord::Base
self.abstract_class = true
end
如果您在从 Rails 5 移动到 Rails 6 后遇到此问题,请确保更改
config.load_defaults 5.2
为了
config.load_defaults 6.0
在您的 config/application.rb
文件中。
我正在在线编写 rails 教程书,当我转到 http://localhost:3000/
时收到以下错误消息"uninitialized constant ApplicationRecord"
它给了我以下突出显示第一行的代码。
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 },
这是我的 application.html.erb 文件:
<!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>
还有我的 user.rb 文件:
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
看来您使用的是 Rails 5 教程,但使用的是 Rails 4。在 Rails 5 中,所有模型都继承自 ApplicationRecord
,而 Rails 4 来自 ActiveRecord::Base
立即修复:
class User < ActiveRecord::Base
...
end
长期修复,切换到 Rails 5 并学习 Rails 5
参考
创建一个名为 app/models/application_record.rb
的新文件,内容如下:
class ApplicationRecord < ActiveRecord::Base
self.abstract_class = true
end
如果您在从 Rails 5 移动到 Rails 6 后遇到此问题,请确保更改
config.load_defaults 5.2
为了
config.load_defaults 6.0
在您的 config/application.rb
文件中。