swift – 将参数传递给方法时出现“调用中的额外参数”错误

概述我试图在 swift中编写以下Objective-C代码： NSCalendar *cal = [NSCalendar currentCalendar];NSDate *now = [NSDate date];NSDate *startOfTheWeek;NSTimeInterval interval;[cal rangeOfUnit:NSWeekCalendarUnit 我试图在 swift中编写以下Objective-C代码：

NSCalendar *cal = [NSCalendar currentCalendar];NSDate *Now = [NSDate date];NSDate *startOfTheWeek;NSTimeInterval interval;[cal rangeOfUnit:NSWeekCalendarUnit        startDate:&startOfTheWeek         interval:&interval          forDate:Now];

它会写本周开始的时候开始的周期和周期间隔.

在我写的 *** 场上

let Now:NSDate = NSDate()var startDate:NSDatevar duration: NSTimeInterval // also trIEd "var duration: CMutablePointer<NSTimeInterval>"let cal = NSCalendar.currentCalendar()cal.rangeOfUnit(unit: NSCalendarUnit.WeekCalendarUnit,startDate: startDate,interval: duration,forDate: Now)"

虽然代码完成告诉我签名是

cal.rangeOfUnit(<#unit: NSCalendarUnit#>,startDate: autoreleasingUnsafePointer<NSDate?>,interval: <#CMutablePointer<NSTimeInterval>#>,forDate: <#NSDate?#>)

在调用中说出额外参数’interval’时出错

我究竟做错了什么？

我也试过了

cal.rangeOfUnit(NSCalendarUnit.WeekCalendarUnit,forDate: Now)

但这会产生错误

“Could not find an overload for ‘rangeOfUnit’ that accepts the supplIEd arguments.”

试试这个：

let Now = NSDate()var startDate: NSDate? = nilvar duration: NSTimeInterval = 0let cal = NSCalendar.currentCalendar()cal.rangeOfUnit(NSCalendarUnit.WeekCalendarUnit,startDate: &startDate,interval: &duration,forDate: Now)

(默认情况下,第一个参数没有外部名称,因此不应该命名.)

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