你如何在objective-c中生成一个随机日期？

Question

我想在两个日期之间生成一个随机日期，例如从今天到 60 天之间的随机日期。我该怎么做？

更新

使用答案中的信息，我想出了这个我经常使用的方法：

// Generate a random date sometime between now and n days before day.
// Also, generate a random time to go with the day while we are at it.
- (NSDate *) generateRandomDateWithinDaysBeforeToday:(NSInteger)days
{
    int r1 = arc4random_uniform(days);
    int r2 = arc4random_uniform(23);
    int r3 = arc4random_uniform(59);

    NSDate *today = [NSDate new];
    NSCalendar *gregorian = 
             [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

    NSDateComponents *offsetComponents = [NSDateComponents new];
    [offsetComponents setDay:(r1*-1)];
    [offsetComponents setHour:r2];
    [offsetComponents setMinute:r3];

    NSDate *rndDate1 = [gregorian dateByAddingComponents:offsetComponents 
                                                  toDate:today options:0];

    return rndDate1;
}

Answer 1

获取一个随机数并将其用作时间间隔，然后将其添加到开始日期。例如

NSTimeInterval timeBetweenDates = [endDate timeIntervalSinceDate:startDate];
NSTimeInterval randomInterval = ((NSTimeInterval)arc4random() / ARC4RANDOM_MAX) * timeBetweenDates;

NSDate *randomDate = [startDate dateByAddingTimeInterval:randomInterval];

Answer 2

1. 生成一个介于 1 到 60 之间的随机数

   int r = arc4random_uniform(60) + 1;
   
   // Usage : arc4random_uniform(hi - lo + 1) + lo
   

2. 获取当前日期

   [NSDate date];
   

3. 使用NSDateComponents 从days 组件中减去随机数并生成新日期。

Answer 3

这里的框架在生成随机日期方面做得很好。但在斯威夫特： https://github.com/thellimist/SwiftRandom/blob/master/SwiftRandom/Randoms.swift

public extension NSDate {
    /// SwiftRandom extension
    public static func randomWithinDaysBeforeToday(days: Int) -> NSDate {
        let today = NSDate()

        guard let gregorian = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian) else {
            print("no calendar \"NSCalendarIdentifierGregorian\" found")
            return today
        }

        let r1 = arc4random_uniform(UInt32(days))
        let r2 = arc4random_uniform(UInt32(23))
        let r3 = arc4random_uniform(UInt32(23))
        let r4 = arc4random_uniform(UInt32(23))

        let offsetComponents = NSDateComponents()
        offsetComponents.day = Int(r1) * -1
        offsetComponents.hour = Int(r2)
        offsetComponents.minute = Int(r3)
        offsetComponents.second = Int(r4)

        guard let rndDate1 = gregorian.dateByAddingComponents(offsetComponents, toDate: today, options: []) else {
            print("randoming failed")
            return today
        }
        return rndDate1
    }

    /// SwiftRandom extension
    public static func random() -> NSDate {
        let randomTime = NSTimeInterval(arc4random_uniform(UInt32.max))
        return NSDate(timeIntervalSince1970: randomTime)
    }

}

Answer 4

这是一个 Swift 4.x 扩展，允许您指定天数，然后它将用于在当前日期之前或之后查找随机的Date。 p>

extension Date {
    static func randomDate(range: Int) -> Date {
        // Get the interval for the current date
        let interval =  Date().timeIntervalSince1970
        // There are 86,400 milliseconds in a day (ignoring leap dates)
        // Multiply the 86,400 milliseconds against the valid range of days
        let intervalRange = Double(86_400 * range)
        // Select a random point within the interval range
        let random = Double(arc4random_uniform(UInt32(intervalRange)) + 1)
        // Since this can either be in the past or future, we shift the range
        // so that the halfway point is the present
        let newInterval = interval + (random - (intervalRange / 2.0))
        // Initialize a date value with our newly created interval
        return Date(timeIntervalSince1970: newInterval)
    }
}

你这样称呼它：

Date.randomDate(range: 500) // Any date that is +/- 500 days from the current date

运行 10 次会产生：

2019-03-15 01:45:52 +0000
2018-12-20 02:09:51 +0000
2018-06-28 10:28:31 +0000
2018-08-02 08:13:01 +0000
2019-01-25 07:04:18 +0000
2018-08-30 22:37:52 +0000
2018-10-05 19:38:22 +0000
2018-11-30 04:51:18 +0000
2019-03-24 07:27:39 +0000

Answer 5

使用秒数。伪代码：

1 Generate a random integer between 0 and (60 * 60 * 24 * 60)
2 Get the unixtime in seconds for the current time
3 Add your random integer
4 Convert this integer back to a date

Answer 6

Swift 3.x +

public extension Date {
    /// SwiftRandom extension
    public static func randomWithinDaysBeforeToday(days: Int) -> Date {
        let today = Date()
        let gregorian = Calendar(identifier: .gregorian)

        let r1 = arc4random_uniform(UInt32(days))
        let r2 = arc4random_uniform(UInt32(23))
        let r3 = arc4random_uniform(UInt32(23))
        let r4 = arc4random_uniform(UInt32(23))

        let offsetComponents = NSDateComponents()
        offsetComponents.day = Int(r1) * -1
        offsetComponents.hour = Int(r2)
        offsetComponents.minute = Int(r3)
        offsetComponents.second = Int(r4)

        let rndDate1 = gregorian.date(byAdding: offsetComponents as DateComponents, to: today)
        return rndDate1!
    }

    /// SwiftRandom extension
    public static func random() -> Date {
        let randomTime = TimeInterval(arc4random_uniform(UInt32.max))
        return Date(timeIntervalSince1970: randomTime)
    }
}

_{附注Esqarrouth's answer 更正了最新的 Swift。}