counter_cache 可以与 has_many 一起使用吗？
我正在努力向我的模型添加 counter_cache：
Users (id, org_id) Orgs (id, users_count)
但出现以下错误： ArgumentError (Unknown key(s): counter_cache):
class Org < ActiveRecord::Base
has_many :users, :counter_cache => true
class User < ActiveRecord::Base
belongs_to :org
任何想法设置错误。我希望 Org.users_count 返回该组织中用户数量的 counter_cache？
I'm working to add a counter_cache to my models:
Users (id, org_id)
Orgs (id, users_count)
But get the following error: ArgumentError (Unknown key(s): counter_cache):
class Org < ActiveRecord::Base
has_many :users, :counter_cache => true
class User < ActiveRecord::Base
belongs_to :org
Any ideas what is setup wrong. I would like Org.users_count to return the counter_cache for the # of users in that org?
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这是行不通的。您必须将 counter_cache 移至 own_to:
并将
users_count字段添加到Org模型中，然后 Rails 将为您更新该字段。不要忘记添加:default=>; 0在迁移中，否则无法正常工作。如果您的应用程序中已经有一些数据并且想要同步计数器，您可以（在迁移后）运行如下所示的操作：
It doesn't work this way. You have to move the counter_cache to the belongs_to:
And add a
users_countfield to theOrgmodel and then Rails will update the field for you. Don't forget to add a:default=> 0in the migration, otherwise it won't work fine.If you have already some data in your app and you want to sync the counter, you can run (after the migration) something like the following: