处理一个ActiveRecord错误，如果数据库是空的 [英] Handling an ActiveRecord error if database is empty

问题描述

我工作的一个轨道4应用程序，我有以下控制器code

I'm working on a rails 4 app, and i have the following controller code

 def index
  @issue = Issue.find(1)
  @sections = @issue.sections
  @articles = @issue.articles
 end

打破，如果数据库是空的，出现错误：找不到问题与ID = 1。什么是正确的方式来检查这一种方式，如果没有在分贝它不会引发错误？

which breaks if the database is empty with the error: "Couldn't find Issue with id=1". What is the proper way to check for this in a way that if nothing is in the db it doesn't raise an error?

推荐答案

您可以使用一个方法是存在活动记录的方法，像这样：

One method you can use is the exists? active record method, like so:

@issue = Issue.where(id: 1)

if @issue.exists?
    # do something if it exists
else
    # do something if it is missing
end

附注：既然你试图查找 ID ，你不一定需要。凡部分;你可以简单地做： Issue.exists（1）

Side note: Since you're attempting to find by id, you don't necessarily need the .where portion; you can simply do: Issue.exists?(1).

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