在swift中，您可以在NSDate中添加扩展方法

extension NSDate {
    func addNoOfDays(noOfDays:Int) -> NSDate! {
        let cal:NSCalendar = NSCalendar.currentCalendar()
        cal.timeZone = NSTimeZone(abbreviation: "UTC")!
        let comps:NSDateComponents = NSDateComponents()
        comps.day = noOfDays
        return cal.dateByAddingComponents(comps, toDate: self, options: nil)
    }
}

你可以用这个

NSDate().addNoOfDays(3)

简单的Swift扩展昨天和明天从任何日期:

extension Date {
    
    var previousDay: Date {
        Calendar.current.date(byAdding: DateComponents(day:-1), to: self)!
    }
    
    var nextDay: Date {
        Calendar.current.date(byAdding: DateComponents(day:+1), to: self)!
    }
    
}

我在这里根据问题中的建议强制展开可选选项: 何时dateByAddingComponents:toDate:options返回nil?

NSDate *now = [NSDate date];
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [calendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:now];
NSDate *startDate = [calendar dateFromComponents:components];
NSLog(@"StartDate = %@", startDate);

components.day += 1;
NSDate *endDate = [calendar dateFromComponents:components];
NSLog(@"EndDate = %@", endDate);

它的工作原理!

NSCalendar *calendar = [NSCalendar currentCalendar];
NSCalendarUnit unit = NSCalendarUnitDay;
NSInteger value = 1;
NSDate *today = [NSDate date];
NSDate *tomorrow = [calendar dateByAddingUnit:unit value:value toDate:today options:NSCalendarMatchStrictly];

NSDate *today=[NSDate date];
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier: NSGregorianCalendar];
NSDateComponents *components=[[NSDateComponents alloc] init];
components.day=1;
NSDate *targetDate =[calendar dateByAddingComponents:components toDate:today options: 0];

在swift中，您可以在NSDate中添加扩展方法

extension NSDate {
    func addNoOfDays(noOfDays:Int) -> NSDate! {
        let cal:NSCalendar = NSCalendar.currentCalendar()
        cal.timeZone = NSTimeZone(abbreviation: "UTC")!
        let comps:NSDateComponents = NSDateComponents()
        comps.day = noOfDays
        return cal.dateByAddingComponents(comps, toDate: self, options: nil)
    }
}

你可以用这个

NSDate().addNoOfDays(3)