从当前日期获取 NSDate 对象 N 秒

新日期的当前日期和时间的秒数。使用负值指定当前日期之前的日期。

为此，我们有一个名为 dateWithTimerIntervalSinceNow(seconds: NSTimeInterval) -> NSDate（Swift）或+ (NSDate*)dateWithTimeIntervalSinceNow:(NSTimeInterval)seconds（Objective-C）的方法。

现在，例如，如果你需要从当前日期和一周到当前日期一周的日期，那么我们可以这样做。

迅速

let totalSecondsInWeek:NSTimeInterval = 7 * 24 * 60 * 60;
//Using negative value for previous date from today
let nextWeek = NSDate().dateWithTimerIntervalSinceNow(totalSecondsInWeek)

//Using positive value for future date from today
let lastWeek = NSDate().dateWithTimerIntervalSinceNow(-totalSecondsInWeek)

Swift 3

let totalSecondsInWeek:TimeInterval = 7 * 24 * 60 * 60;

//Using positive value to add to the current date
let nextWeek = Date(timeIntervalSinceNow: totalSecondsInWeek)

//Using negative value to get date one week from current date
let lastWeek = Date(timeIntervalSinceNow: -totalSecondsInWeek)

Objective-C

NSTimeInterval totalSecondsInWeek = 7 * 24 * 60 * 60;
//Using negative value for previous date from today
NSDate *lastWeek = [NSDate dateWithTimeIntervalSinceNow:-totalSecondsInWeek];

//Using positive value for future date from today
NSDate *nextWeek = [NSDate dateWithTimeIntervalSinceNow:totalSecondsInWeek];

NSLog(@"Last Week: %@", lastWeek);
NSLog(@"Right Now: %@", now);
NSLog(@"Next Week: %@", nextWeek);