在Rails 5中，当我根据其中一个字段搜索模型时，为什么会得到未定义的find_by方法？

II'm using Rails 5. I want to search for a model based on a user_id field. My table looks like this

我正在使用Rails 5.我想基于user_id字段搜索模型。我的桌子看起来像这样

cindex=# \d user_notifications;
                               Table "public.user_notifications"
       Column       |  Type   |                            Modifiers
--------------------+---------+-----------------------------------------------------------------
 id                 | integer | not null default nextval('user_notifications_id_seq'::regclass)
 user_id            | integer |
 crypto_currency_id | integer |
 price              | integer | not null
 buy  

          | boolean | not null

but when I attempt to look up a model like so

但是当我试图查找这样的模型时

 @user_notification = UserNotification.find_by_user(current_user)

I get the error

我收到了错误

undefined method `find_by_user' for UserNotification:Class

What's the simple (Rails) way to look up my field?

查看我的领域的简单（Rails）方法是什么？

2 个解决方案

#1

find_by_user is not a built in method in rails, you would have to define it in your model.

find_by_user不是rails中的内置方法，您必须在模型中定义它。

What you should use to find a record by it's id is simply Find. It will return one record matching the inputed id if it exists.

您应该使用它来查找记录的id是简单的查找。它将返回一个匹配输入id的记录（如果存在）。

Ex:

例如：

@user_notification = UserNotifaction.find(1)

And to find by a specific field, such as a custom id, use find_by

要通过特定字段（例如自定义ID）查找，请使用find_by

@user_notification = UserNotifaction.find_by(custom_id: 1)

#2

@user_notification = UserNotification.find_by_user_id(current_user.id)

#1