获取当前是今年的第几周

  NSCalendar * calendar = [NSCalendarcurrentCalendar];

    NSDate * currentDate = [NSDatedate];

    NSInteger week = [calendarordinalityOfUnit:NSCalendarUnitWeekdayinUnit:NSCalendarUnitYearforDate:currentDate];

    NSLog(@"今天是今年的第%ld周",week);