Swift 3.0 无法获取所需的对象指针(替换 NULL)：无法加载'self'，因为无法计算其值

Question

执行以下代码:

public enum Month : String {
    case January  = "JAN"
    case February = "FEB"
    case March = "MAR"
    case April = "APR"
    case May = "MAY"
    case June = "JUN"
    case July = "JUL"
    case August = "AUG"
    case September = "SEP"
    case October = "OCT"
    case November = "NOV"
    case December = "DEC"
    func toDate() -> Date {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "dd.MMM.yyyy hh:mm a"
        let dateString = "01.(self.rawValue).2016 12:00 PM"
        return dateFormatter.date(from: dateString)!
    }
}

我:

致命错误:在展开可选值

时意外发现nil

当我尝试打印po dateFormatter。date(from: dateString)!"发生崩溃的地方:

致命错误:在展开可选值时意外发现nil错误:警告:无法获得所需的对象指针(替换为NULL):无法加载"self"，因为它的值无法求值

错误:Execution was interrupted, reason: EXC_BREAKPOINT (code=1, subcode=0x100c551ec)。进程已返回到表达式求值前的状态。

这只发生在我运行iOS 10.1.1的iPhone 6s上，而不会发生在任何模拟器和运行iOS 9.x.x的设备上

有人知道发生了什么事，以及"无法加载'self'，因为它的值无法评估"是什么意思吗?

我用这段代码在一个新项目中尝试了它，我仍然可以重现错误。

即使硬编码月份，没有self部分也会产生相同的错误:

let dateString = "01.NOV.2016 12:00 PM"

构造Date对象的正确方法是:

let calendar = Calendar.current
var components = DateComponents()
components.day = 1
components.month = month
components.year = year
components.hour = 12
components.minute = 00
let date = calendar.date(from: components)!

Answer 1

对于后面的任何人来说，当您只有月份和年份时，构造Date对象的正确方法是:

var components = DateComponents()
components.day = 1
components.month = month
components.year = year
components.hour = 12
components.minute = 00
let date = Calendar.current.date(from: components)

Answer 2

您的代码将在不到两个月的时间内给出完全错误的结果。如果用户的语言环境不是说英语，它就会崩溃。