ruby-on-rails - Creating a Rails model's child when necessary

Question

I have a live site that has many Book models. I've recently added a Settings model that belongs_to each Book.

Now when I'm writing code to use the book.settings method, how do I avoid checking ‘book.settings.nil?’ or doing ’book.settings || book.create_settings’ in every call? The settings model has some defaults I can use.

Answer 1

更新：较早的答案建议使用后提交挂钩将默认设置添加到书籍。根据评论，这不是问题。我已经删除了较早的答案，以避免读者混淆。

您可以使用将在生产服务器上运行一次的 rake 任务来修复没有默认设置的书籍。

Answer 2

为什么不将这些条件放在自定义方法上，并调用它而不是调用settings，如下所示：

def default_settings
  self.settings || self.create_settings
end

然后你这样称呼它：

@book.default_settings

nil?里面也可以查default_settings。