您收到一条错误消息，因为0它不是的有效值NSCalendarOptions。对于“无选项”，请使用NSCalendarOptions(0)或简单地nil：
let ageComponents = calendar.components(.CalendarUnitYear,
fromDate: birthday,
toDate: Now,
options: nil)
let age = ageComponents.year
（指定nil是可能的，因为它NSCalendarOptions符合RawOptionSetType从继承的协议NilLiteralConvertible。）
let ageComponents = calendar.components(.Year,
fromDate: birthday,
toDate: Now,
options: [])
假设使用Swift 3类型Date和Calendar：
let Now = Date()
let birthday: Date = ...
let calendar = Calendar.current
let ageComponents = calendar.dateComponents([.year], from: birthday, to: Now)
let age = ageComponents.year!
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