是否可以否定 Rails 3 中的范围? [英] Is it possible to negate a scope in Rails 3?

问题描述

我的类具有以下范围，称为 Collection:

I have the following scope for my class called Collection:

scope :with_missing_coins, joins(:coins).where("coins.is_missing = ?", true)

我可以运行 Collection.with_missing_coins.count 并返回结果——效果很好！目前，如果我想在不丢失硬币的情况下获得收藏，我会添加另一个范围:

I can run Collection.with_missing_coins.count and get a result back -- it works great! Currently, if I want to get collections without missing coins, I add another scope:

scope :without_missing_coins, joins(:coins).where("coins.is_missing = ?", false)

我发现自己写了很多这些相反"的范围.是否有可能在不牺牲可读性或诉诸 lambda/方法(以 true 或 false 作为参数)的情况下获得作用域的反面?

I find myself writing a lot of these "opposite" scopes. Is it possible to get the opposite of a scope without sacrificing readability or resorting to a lambda/method (that takes true or false as a parameter)?

像这样:

Collection.!with_missing_coins

推荐答案

我不会为此使用单一作用域，而是使用两个作用域:

I wouldn't use a single scope for this, but two:

scope :with_missing_coins, joins(:coins).where("coins.is_missing = ?", true)
scope :without_missing_coins, joins(:coins).where("coins.is_missing = ?", false)

这样，当使用这些作用域时，就会清楚地知道发生了什么.根据 numbers1311407 的建议，尚不清楚 with_missing_coins 的 false 参数在做什么.

That way, when these scopes are used then it's explicit what's happening. With what numbers1311407 suggests, it is not immediately clear what the false argument to with_missing_coins is doing.

我们应该尽量写出尽可能清晰的代码，如果这意味着不那么热衷于 DRY，那么就这样吧.

We should try to write code as clear as possible and if that means being less of a zealot about DRY once in while then so be it.

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