获取当前日期 所在的周

/// 获取当前日期 所在的周
func getWeekTime(_ dateStr: String) -> Array<String> {
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyyMMdd"
let nowDate = dateFormatter.date(from: dateStr)
let calendar = Calendar.current
let comp = calendar.dateComponents([.year, .month, .day, .weekday], from: nowDate!)

      // 获取今天是周几
      let weekDay = comp.weekday
      // 获取几天是几号
      let day = comp.day
        
      // 计算当前日期和本周的星期一和星期天相差天数
      var firstDiff: Int
      var lastDiff: Int
      // weekDay = 1;
      if (weekDay == 1) {
          firstDiff = -6;
          lastDiff = 0;
      } else {
          firstDiff = calendar.firstWeekday - weekDay! + 1
          lastDiff = 8 - weekDay!
      }
       
      // 在当前日期(去掉时分秒)基础上加上差的天数
      var firstDayComp = calendar.dateComponents([.year, .month, .day], from: nowDate!)
      firstDayComp.day = day! + firstDiff
      let firstDayOfWeek = calendar.date(from: firstDayComp)
      var lastDayComp = calendar.dateComponents([.year, .month, .day], from: nowDate!)
      lastDayComp.day = day! + lastDiff
      let lastDayOfWeek = calendar.date(from: lastDayComp)
        
      let firstDay = dateFormatter.string(from: firstDayOfWeek!)
      let lastDay = dateFormatter.string(from: lastDayOfWeek!)
      let weekArr = [firstDay, lastDay]
        
      return weekArr;
  }