ruby-on-rails - NameError:未初始化的常量ApplicationRecord

Question

我收到上述错误，但是我相信我使用的是Rails 5:

turlingdrome$ rails -v
/Users/brianp/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/railties-5.2.3/lib/rails/app_loader.rb:53: warning: Insecure world writable dir /Users/brianp/work in PATH, mode 040777
Rails 5.2.0

turlingdrome$ rake db:migrate
rake aborted!
NameError: uninitialized constant ApplicationRecord
/Users/brianp/work/online-reporting/app/models/client.rb:1:in `<top (required)>'
/Users/brianp/work/online-reporting/config/routes.rb:7:in `block in <top (required)>'
/Users/brianp/work/online-reporting/config/routes.rb:1:in `<top (required)>'
/Users/brianp/work/online-reporting/config/environment.rb:5:in `<top (required)>'
Tasks: TOP => db:migrate => db:load_config => environment
(See full trace by running task with --trace)

我不认为--trace有用...但是可以根据需要附加它...

Answer 1

在版本5之前，Rails生成了从ActiveRecord::Base继承的模型。

# rails g model foo.
class Foo < ActiveRecord::Base

end

Rails 5引入了 ApplicationRecord，它是等效于 ApplicationController的模型。因此在Rails 5上会生成以下内容:

# rails g model foo.
class Foo < ApplicationRecord

end

当您运行 rails new时，将生成ApplicationRecord类本身。

但是，这没有什么神奇的-它只是根深蒂固的惯例。

# app/models/application_record.rb
class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
end

如果您正在获取 NameError: uninitialized constant ApplicationRecord，则要么升级到Rails 5而不创建它，要么误删除了它。解决方案只是创建文件。