如何将日期“MM-dd-yyyy hh：mm：ss a”转换为文字格式？

Question

我想创建一个将日期转换成文本格式，如“刚才，2分钟，1小时，1天，10月10日”的功能。这里就是我在得到一个错误，我的示例代码：

let components = cal.components([.Day,.Hour,.Minute], fromDate: date, toDate: NSDate(), options:[]) 

这里是我的全码：

func getTextToDisplayFormattingDate(date: NSDate) -> String { 
    var textToDisplay = "" 
    let dateFormatter = DateFormatter() 
    dateFormatter.dateFormat = "MM-dd-yyyy hh:mm:ss a" 
    dateFormatter.timeZone = TimeZone(identifier: "UTC") 

    let cal = NSCalendar.current 

    let components = cal.components([.Day,.Hour,.Minute], fromDate: date, toDate: NSDate(), options:[]) 

    switch components.day { 
    case 0: 
     if components.hour == 0 { 
      if components.minute <= 0 { 
       textToDisplay = "just now " 
      } else { 
       textToDisplay = "\(components.minute) min" 
      } 
     } else { 
      textToDisplay = "\(components.hours) hrs" 
     } 
    case 1...6: 
     textToDisplay = "\(components.day) d" 
    default: 
     dateFormatter.dateFormat = "MMM dd" 
     textToDisplay = dateFormatter.string(from: date as Date) 
    } 

    return textToDisplay 
} 

Answer 1

其实，这是难以计算的日，时，分日期由NSCalendar.components 2之间，你的程序会导致意想不到的结果。通常，我们通过它们之间的TimeInterval进行计算。在SWIFT 3.2或SWIFT 4.0试试这个：

func getTextToDisplayFormattingDate(date: Date) -> String { 
    var textToDisplay = "" 

    let now = Date() 
    let timeInterval = now.timeIntervalSince(date) 
    if timeInterval < 60 { 
     textToDisplay = "just now " 
    } 
    else if timeInterval < 60 * 60 { 
     textToDisplay = "\(Int(timeInterval/60)) min" 
    } 
    else if timeInterval < 60 * 60 * 24 { 
     textToDisplay = "\(Int(timeInterval/60/60)) hrs" 
    } 
    else { 
     let dateFormatter = DateFormatter() 
     dateFormatter.timeZone = TimeZone(identifier: "UTC") 

     if timeInterval < 60 * 60 * 24 * 6 { //less than 6 days 
      // For getting days 
      // textToDisplay = "\(Int(timeInterval/60/60/24)) d" 

      // For getting weekday name 
      dateFormatter.dateFormat = "EEEE" 
      textToDisplay = dateFormatter.string(from: date) //weekday name 
     } 
     else{ 
      dateFormatter.dateFormat = "MMM dd" 
      textToDisplay = dateFormatter.string(from: date as Date) 
     } 
    } 

    return textToDisplay 
} 

记住使用常量来替换表示喜欢60 * 60 * 24以提高性能。

Answer 2

使用这样的：

的变化在我的代码：

1. 在地方NSDate，我用Date。
2. 在地方NSCalendar我用Calendar
3. components(_:from:to:options:)已更名为dateComponents(_:from:to:)

4. components值一样day, minute, hour是optional。这就是为什么我添加检查之前切换。

   func getTextToDisplayFormattingDate(date: Date) -> String { 
       var textToDisplay = "" 
       let dateFormatter = DateFormatter() 
       dateFormatter.dateFormat = "MM-dd-yyyy hh:mm:ss a" 
       dateFormatter.timeZone = TimeZone(identifier: "UTC") 
   
       let cal = Calendar.current 
       let components = cal.dateComponents([.day, .hour , .minute], from: date, to: Date()) 
   
       if let day = components.day, let minute = components.minute, let hour = components.hour { 
        switch day { 
        case 0: 
         if hour == 0 { 
          if minute <= 0 { 
           textToDisplay = "just now " 
          } else { 
           textToDisplay = "\(minute) min" 
          } 
         } else { 
          textToDisplay = "\(hour) hrs" 
         } 
        case 1...6: 
         textToDisplay = "\(day) d" 
        default: 
         dateFormatter.dateFormat = "MMM dd" 
         textToDisplay = dateFormatter.string(from: date) 
        } 
       } 
       return textToDisplay 
   }