Swift 3 中的日期扩展

Posted 2023-02-24

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【中文标题】Swift 3 中的日期扩展【英文标题】：Date Extensions in Swift 3 【发布时间】：2016-09-05 16:44:39 【问题描述】：

以下代码是日期扩展的一部分。但是，在 Swift 3 中，我遇到了一些不会消失的错误。我已经把“NSCalendar”改成了“Calendar”：

func startOfWeek(_ weekday: Int?) -> Date? 
    guard
        let cal = Calendar.current,
        let comp: DateComponents = (cal as Calendar).components([.yearForWeekOfYear, .weekOfYear], from: self) else  return nil 
    comp.to12pm()
    cal.firstWeekday = weekday ?? 1
    return cal.date(from: comp)!

func endOfWeek(_ weekday: Int) -> Date? 
    guard
        let cal = Calendar.current,
        var comp: DateComponents = (cal as Calendar).components([.weekOfYear], from: self) else  return nil 
    comp.weekOfYear = 1
    comp.day -= 1
    comp.to12pm()
    return (cal as NSCalendar).date(byAdding: comp, to: self.startOfWeek(weekday)!, options: [])!

第 3 行和第 11 行： 让 cal = Calendar.current，条件绑定的初始值设定项必须是 Optional 类型，而不是 'Calendar'

第 12 行：我有一个错误，但通过将“let comp:”更改为“var comp:”来修复它

第 14 行： comp.day -= 1 错误：二元运算符“-=”不能应用于“Int？”类型的操作数和“诠释”

我不擅长扩展，这段代码改编自我在网上找到的一个扩展，所以现在更新它被证明是困难的。有什么建议吗？

疑难解答（我尝试过的事情）：

让 cal = Calendar?.current,

错误：键入“日历？”没有成员“当前”

let cal：日历？ = 日历.当前，

错误：明确指定类型“日历？”为初始化器添加了额外的可选级别，使可选检查始终成功

让 cal = Calendar.current?,

错误：不能对“日历”类型的非可选值使用可选链接

【问题讨论】：

你应该按照编译器告诉你的去做。有些类型是可选的，现在它们不是：删除你的可选绑定。它告诉你结构应该是可变的：做它然后看看它现在是如何工作的。等等。 @EricAya 我尝试了 let cal：'日历？ = Calendar.current' 以及 'let cal = Calendar?.current' 和 'let cal = Calendar.current?'但没有一个工作。那么如何让日历成为可选的呢？只是一个猜测，comp.day -= 1 comp.day 不是左值，它只是一个名为 day 的方法的返回值...在 Objective-C 中，有一些魔法可以制作属性以这种方式工作（即它与经典 obj c 对象的点访问器不同），也许在 swift 3 中该魔法已关闭试试

func startOfWeek(_ weekday: Int? = 1) -&gt; Date?          var cal = Calendar.current         cal.firstWeekday = weekday ?? 1         let comp = cal.dateComponents([.yearForWeekOfYear, .weekOfYear], from: self)         return cal.date(from: comp)

@LeoDabus 谢谢，我发布了修改后的代码作为答案并感谢你。 【参考方案1】：

我在 Swift 3 中的日期扩展，基于来自 @LeoDabus 的 cmets

func startOfWeek(_ weekday: Int? = 1) -> Date? 
    var cal = Calendar.current
    cal.firstWeekday = weekday ?? 1
    let comp = cal.dateComponents([.yearForWeekOfYear, .weekOfYear], from: self)
    comp.to12pm()
    return cal.date(from: comp)

func endOfWeek(_ weekday: Int) -> Date? 
    let cal = Calendar.current
    var comp = cal.dateComponents([.weekOfYear], from: self)
    comp.weekOfYear = 1
    comp.day? -= 1
    comp.to12pm()
    return cal.date(byAdding: comp, to: self.startOfWeek(weekday)!)!

请注意，我仍处于迁移中期，因此我只能确认这些已消除错误并且还不能在生产中测试它们。

【讨论】：

【参考方案2】：

您可以使用此扩展程序分别获取每个日期组件：

extension Date 

// MARK:- APP SPECIFIC FORMATS

func app_dateFromString(strDate:String, format:String) -> Date? 

    let dateFormatter:DateFormatter = DateFormatter()
    dateFormatter.dateFormat = format
    if let dtDate = dateFormatter.date(from: strDate)
        return dtDate as Date?
    
    return nil



func app_stringFromDate() -> String
    let dateFormatter:DateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
    let strdt = dateFormatter.string(from: self as Date)
    if let dtDate = dateFormatter.date(from: strdt)
        return dateFormatter.string(from: dtDate)
    
    return "--"


func app_stringFromDate_timeStamp() -> String
    return "\(self.hourTwoDigit):\(self.minuteTwoDigit) \(self.AM_PM)  \(self.monthNameShort) \(self.dayTwoDigit)"



func getUTCFormateDate(localDate: NSDate) -> String 

    let dateFormatter:DateFormatter = DateFormatter()
    let timeZone: NSTimeZone = NSTimeZone(name: "UTC")!
    dateFormatter.timeZone = timeZone as TimeZone!
    dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm"
    let dateString: String = dateFormatter.string(from: localDate as Date)
    return dateString



func combineDateWithTime(date: NSDate, time: NSDate) -> NSDate? 
    let calendar = NSCalendar.current


    let dateComponents = calendar.dateComponents([.year, .month, .day], from: date as Date)

    let timeComponents = calendar.dateComponents([.hour, .minute, .second], from: time as Date)


    let mergedComponments = NSDateComponents()
    mergedComponments.year = dateComponents.year!
    mergedComponments.month = dateComponents.month!
    mergedComponments.day = dateComponents.day!
    mergedComponments.hour = timeComponents.hour!
    mergedComponments.minute = timeComponents.minute!
    mergedComponments.second = timeComponents.second!

    return calendar.date(from: mergedComponments as DateComponents) as NSDate?


func getDatesBetweenDates(startDate:NSDate, andEndDate endDate:NSDate) -> [NSDate] 
    let gregorian: NSCalendar = NSCalendar.current as NSCalendar;
    let components = gregorian.components(NSCalendar.Unit.day, from: startDate as Date, to: endDate as Date, options: [])
    var arrDates = [NSDate]()
    for i in 0...components.day!
        arrDates.append(startDate.addingTimeInterval(60*60*24*Double(i)))
    
    return arrDates



func isGreaterThanDate(dateToCompare: NSDate) -> Bool 
    //Declare Variables
    var isGreater = false

    //Compare Values
    if self.compare(dateToCompare as Date) == ComparisonResult.orderedDescending 
        isGreater = true
    

    //Return Result
    return isGreater


func isLessThanDate(dateToCompare: Date) -> Bool 
    //Declare Variables
    var isLess = false

    //Compare Values
    if self.compare(dateToCompare as Date) == ComparisonResult.orderedAscending 
        isLess = true
    

    //Return Result
    return isLess


func equalToDate(dateToCompare: NSDate) -> Bool 
    //Declare Variables
    var isEqualTo = false

    //Compare Values
    if self.compare(dateToCompare as Date) == ComparisonResult.orderedSame 
        isEqualTo = true
    

    //Return Result
    return isEqualTo



// MARK:- TIME
var timeWithAMPM: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "h:mma"
    dateFormatter.amSymbol = "am"
    dateFormatter.pmSymbol = "pm"
    return dateFormatter.string(from: self as Date)





// MARK:- YEAR


var yearFourDigit_Int: Int 
    return Int(self.yearFourDigit)!


var yearOneDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "y"
    return dateFormatter.string(from: self as Date)

var yearTwoDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yy"
    return dateFormatter.string(from: self as Date)

var yearFourDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy"
    return dateFormatter.string(from: self as Date)




// MARK:- MONTH

var monthOneDigit_Int: Int 
    return Int(self.monthOneDigit)!

var monthTwoDigit_Int: Int 
    return Int(self.monthTwoDigit)!



var monthOneDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "M"
    return dateFormatter.string(from: self as Date)

var monthTwoDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "MM"
    return dateFormatter.string(from: self as Date)

var monthNameShort: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "MMM"
    return dateFormatter.string(from: self as Date)

var monthNameFull: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "MMMM"
    return dateFormatter.string(from: self as Date)

var monthNameFirstLetter: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "MMMMM"
    return dateFormatter.string(from: self as Date)


// MARK:- DAY

var dayOneDigit_Int: Int 
    return Int(self.dayOneDigit)!

var dayTwoDigit_Int: Int 
    return Int(self.dayTwoDigit)!


var dayOneDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "d"
    return dateFormatter.string(from: self as Date)

var dayTwoDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "dd"
    return dateFormatter.string(from: self as Date)

var dayNameShort: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "E"
    return dateFormatter.string(from: self as Date)

var dayNameFull: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "EEEE"
    return dateFormatter.string(from: self as Date)

var dayNameFirstLetter: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "EEEEE"
    return dateFormatter.string(from: self as Date)





// MARK:- AM PM
var AM_PM: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "a"
    return dateFormatter.string(from: self as Date)


// MARK:- HOUR


var hourOneDigit_Int: Int 
    return Int(self.hourOneDigit)!

var hourTwoDigit_Int: Int 
    return Int(self.hourTwoDigit)!

var hourOneDigit24Hours_Int: Int 
    return Int(self.hourOneDigit24Hours)!

var hourTwoDigit24Hours_Int: Int 
    return Int(self.hourTwoDigit24Hours)!

var hourOneDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "h"
    return dateFormatter.string(from: self as Date)

var hourTwoDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "hh"
    return dateFormatter.string(from: self as Date)

var hourOneDigit24Hours: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "H"
    return dateFormatter.string(from: self as Date)

var hourTwoDigit24Hours: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "HH"
    return dateFormatter.string(from: self as Date)


// MARK:- MINUTE

var minuteOneDigit_Int: Int 
    return Int(self.minuteOneDigit)!

var minuteTwoDigit_Int: Int 
    return Int(self.minuteTwoDigit)!


var minuteOneDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "m"
    return dateFormatter.string(from: self as Date)

var minuteTwoDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "mm"
    return dateFormatter.string(from: self as Date)



// MARK:- SECOND

var secondOneDigit_Int: Int 
    return Int(self.secondOneDigit)!

var secondTwoDigit_Int: Int 
    return Int(self.secondTwoDigit)!


var secondOneDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "s"
    return dateFormatter.string(from: self as Date)

var secondTwoDigit: String 
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "ss"
    return dateFormatter.string(from: self as Date)

【讨论】：

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