Swift 3 – UTC到前一刻标签，思考12h / 24h设备时间的变化

我想将timeUTC转换为“5s前”。 前面的标签也在想着12h / 24h的变化。 因为崩溃。 现在下面的代码返回标签值行我想在游乐场。 但不是在我的ios项目。 它不会进入If块。 我错过了什么或者有什么问题？

let dateStringUTC = "2016-10-22 12:37:48 +0000" let dateFormatter = DateFormatter() dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss ZZZ" if let from = dateFormatter.date(from: dateStringUTC) { dateFormatter.dateFormat = "MMM d, yyyy h:mm:ss a" let stringFromDate = dateFormatter.string(from: from) let dateLast = dateFormatter.date(from: stringFromDate) let now = Date() let components: NSCalendar.Unit = [.second, .minute, .hour, .day, .weekOfMonth] let difference = (Calendar.current as NSCalendar).components(components, from: dateLast!, to: now, options: []) if difference.second! <= 0 { self.timeInfoLbl.text = "now" } if difference.second! > 0 && difference.minute! == 0 { self.timeInfoLbl.text = String(describing: difference.second!) + "s." } if difference.minute! > 0 && difference.hour! == 0 { self.timeInfoLbl.text = String(describing: difference.minute!) + "m." } if difference.hour! > 0 && difference.day! == 0 { self.timeInfoLbl.text = String(describing: difference.hour!) + "h." } if difference.day! > 0 && difference.weekOfMonth! == 0 { self.timeInfoLbl.text = String(describing: difference.day!) + "d." } if difference.weekOfMonth! > 0 { self.timeInfoLbl.text = String(describing: difference.weekOfMonth!) + "w." if difference.weekOfMonth! > 52 { let number = Float(difference.weekOfMonth!) / 52 let strYear = String(format:"%.1f", number) self.timeInfoLbl.text = strYear + " year" } } } 

Answer 1

要将此string转换为date，我会这样做：

 let dateStringUTC = "2016-10-22 12:37:48 +0000" let dateFormatter = DateFormatter() dateFormatter.locale = Locale(identifier: "en_US_POSIX") dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss X" let date = dateFormatter.date(from: dateStringUTC)! 

然后，以一个很好的格式显示stream逝的时间，考虑DateComponentsFormatter ，例如：

 let now = Date() let formatter = DateComponentsFormatter() formatter.unitsStyle = .full formatter.maximumUnitCount = 2 let string = formatter.string(from: date, to: Date())! + " " + NSLocalizedString("ago", comment: "added after elapsed time to say how long before")