`load_missing_constant'：在自动加载常量 ApplicationRecord (RuntimeError) 时检测到循环依赖

Question

After Upgrading from Rails 4.2 to Rails 5.0, I received this error:

`load_missing_constant': Circular dependency detected while autoloading constant ApplicationRecord (RuntimeError) 

Answer 1

This is such a simple thing to miss so I thought I should mentioned it.

If you tried to "Auto Replace" all of your models from:

class Model < ActiveRecord::Base

to

class Model < ApplicationRecord

chances are, you probably replaced your app/models/application_record.rb file with the same, and it looks like this right now:

class ApplicationRecord < ApplicationRecord

fix it back to read:

class ApplicationRecord < ActiveRecord::Base

and you should be good to go!