swift 日期的相关处理

最近处理了一些关于日期的问题，先记下来，可以后来查用。

1，将字符串转化为日期

let formatter = DateFormatter.init()

formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

let lastTime = formatter.date(from:lastTimeString!)

2，将日期转化为字符串

let date = Date()

let  timeFormatter = DateFormatter()

timeFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

let currentTime = timeFormatter.string(from: date as Date) as String 

3，得到两个日期的差值

a,通过和格林威治时间比较，得到向差的秒数

let lastTime = formatter.date(from:lastTimeString!)

let currentTime = formatter.date(from:self.getCurrentTimeStamp())

let timeInterval = (currentTime?.timeIntervalSince1970)! - (lastTime?.timeIntervalSince1970)!

b,通过比较，得到相差的年月日时分秒

let ctime = date

let mtime = date2

let ctimedf = DateFormatter()

ctimedf.dateFormat = "yyyy-MM-dd HH:mm:ss"

let ctimeDate = ctimedf.date(from: ctime)

let mtimeDate = ctimedf.date(from: mtime)

let calendar = Calendar.current

let unitFlags:NSCalendar.Unit = [NSCalendar.Unit.year, NSCalendar.Unit.month , NSCalendar.Unit.day , NSCalendar.Unit.hour , NSCalendar.Unit.minute , NSCalendar.Unit.second]

let components = (calendar as NSCalendar).components(unitFlags, from: ctimeDate!, to: mtimeDate!, options: NSCalendar.Options.init(rawValue: 0))

components.hour!

components.day

components.second

components.minute!

4,获取当前时间的时分秒

let calendar: Calendar = Calendar(identifier: .gregorian)

var comps: DateComponents = DateComponents()

 comps = calendar.dateComponents([.year,.month,.day, .weekday, .hour, .minute,.second], from: Date())

let hour = comps.hour!            // 小时

 let minutes = comps.minute!          // 分钟