[swift-users] How do I find really detailed information about changes?

[Brent Royal-Gordon]

> I'm now trying to find why, along with changing from NSCalendar to Calendar, the .components are optional. I can't find any mention of it, and I'm not sure in what situation minutes or hours could be nil and how I should guard against it.

In Objective-C, these properties can be `NSUndefinedDateComponent`. In Swift, that's represented as `nil` instead.

Essentially, this happens when you don't request a particular date component—for instance, when you say `gregorian.components([.year, .month, .day], fromDate: date)`, `hours` and `minutes` will be `nil`. In Objective-C, they would have been `NSUndefinedDateComponent`.

-- 
Brent Royal-Gordon
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