(first noticed on: Xcode 8.2.1, iOS 10, Swift 3) (still present as of: Xcode 9 beta 3, iOS11, Swift 4)
（首先注意到：Xcode 8.2.1，iOS 10，Swift 3）（仍然存在：Xcode 9 beta 3，iOS11，Swift 4）
We all know that the Core Data concept of optionals precedes and is not strictly tied to the Swift concept of optionals.
我们都知道，期权的核心数据概念先于并不严格依赖于Swift的期权概念。
And we have accepted that even if a Core Data attribute is marked as Non-optional, the auto-generated NSManagedObject subclass has an optional type:
我们已经接受了即使Core Data属性被标记为Non-optional，自动生成的NSManagedObject子类也有一个可选类型：
(some people manually remove the ? with no adverse effects, some don't, but that's beside the point)
（有些人手动删除？没有任何不利影响，有些人没有，但这不是重点）
(From here on the example and screenshots are for Bool properties, but same goes for Int16/32/64, Double, Float)
（从这里开始的示例和屏幕截图是针对Bool属性的，但同样适用于Int16 / 32/64，Double，Float）
Now I noticed the reverse - when a Core Data attribute of type Bool is marked as Optional (and Use Scalar Type is chosen, which Xcode does by default), the auto-generated class has a variable of a non-optional type.
现在我注意到了相反的情况 - 当Bool类型的Core Data属性被标记为Optional（并且选择了Use Scalar Type，Xcode默认执行）时，自动生成的类具有非可选类型的变量。
Does this make sense? Is it a bug? Is the behaviour documented anywhere?
这有意义吗？这是一个错误吗？行为记录在任何地方吗？
And most importantly - how do I actually represent an optional Bool?
最重要的是 - 我如何实际代表一个可选的Bool？
I can think of some work-arounds, but they don't seem ideal (e.g. not using scalars, but going back to NSNumber representation of the Bool. Or (even worse) having a separate Bool called something like isVerified_isSet)
我可以想到一些解决方法，但它们似乎并不理想（例如，不使用标量，而是回到Bool的NSNumber表示。或者（甚至更糟）有一个叫做isVerified_isSet的单独的Bool）
Note: I did a couple more tests and if the Default Value is set to None or to NO, then the variable gets saved as false (even if I never actually assign it in my code). If the Default Value is set to YES, then the variable gets saved as true. Still, this means that (apparently) there is no way to logically represent this variable as not having been set yet.
注意：我做了几个测试，如果默认值设置为None或NO，那么变量将保存为false（即使我从未在我的代码中实际分配它）。如果“默认值”设置为“是”，则变量将保存为true。尽管如此，这意味着（显然）没有办法在逻辑上将此变量表示为尚未设置。
2 个解决方案
#1
12
I see the same thing, and I consider it to be a bug. It's not documented anywhere that I can find. Apparently Core Data is applying Objective-C style assumptions here, where a boolean defaults to NO, and an integer defaults to 0. The Core Data/Swift interface has some rough edges, and this is one I hadn't considered before.
我看到同样的事情，我认为这是一个错误。它没有记录在我能找到的任何地方。显然Core Data正在应用Objective-C样式假设，其中布尔值默认为NO，整数默认为0.核心数据/ Swift接口有一些粗糙的边缘，这是我之前没有考虑过的。
It's a good find but I think you're stuck with it until Apple addresses it. You already know the best workarounds, which I agree aren't great. I recommend filing a bug.
这是一个很好的发现，但我认为你坚持使用它直到Apple解决它。你已经知道最好的解决方法，我同意这不是很好。我建议提交一个bug。
#2
5
This happens because Objective-C scalar types do not have a notion of nil value. Source: handling-core-data-optional-scalar-attributes
这是因为Objective-C标量类型没有nil值的概念。来源：handling-core-data-optional-scalar-attributes
#1
12
I see the same thing, and I consider it to be a bug. It's not documented anywhere that I can find. Apparently Core Data is applying Objective-C style assumptions here, where a boolean defaults to NO, and an integer defaults to 0. The Core Data/Swift interface has some rough edges, and this is one I hadn't considered before.
我看到同样的事情，我认为这是一个错误。它没有记录在我能找到的任何地方。显然Core Data正在应用Objective-C样式假设，其中布尔值默认为NO，整数默认为0.核心数据/ Swift接口有一些粗糙的边缘，这是我之前没有考虑过的。
It's a good find but I think you're stuck with it until Apple addresses it. You already know the best workarounds, which I agree aren't great. I recommend filing a bug.
这是一个很好的发现，但我认为你坚持使用它直到Apple解决它。你已经知道最好的解决方法，我同意这不是很好。我建议提交一个bug。
#2
5
This happens because Objective-C scalar types do not have a notion of nil value. Source: handling-core-data-optional-scalar-attributes
这是因为Objective-C标量类型没有nil值的概念。来源：handling-core-data-optional-scalar-attributes