Objective c 根据过去的NSDate和重复间隔，计算从现在开始的下一个事件
如何通过重复某个时间间隔，从过去的某个日期计算比现在晚的第一个日期？例如：Objective c 根据过去的NSDate和重复间隔，计算从现在开始的下一个事件,objective-c,cocoa,cocoa-touch,nsdate,date-arithmetic,Objective C,Cocoa,Cocoa Touch,Nsdate,Date Arithmetic,如何通过重复某个时间间隔，从过去的某个日期计算比现在晚的第一个日期？例如： // Date in the past NSDate *pastDate = [NSDate my_dateWithString:@"11/09/2001"]; // Time interval NSTimeInterval repeatInterval = 14 * 24 * 60 * 60; // 2 weeks // Current date NSDate *now = [NSDate date]; // 23
// Date in the past
NSDate *pastDate = [NSDate my_dateWithString:@"11/09/2001"];
// Time interval
NSTimeInterval repeatInterval = 14 * 24 * 60 * 60; // 2 weeks
// Current date
NSDate *now = [NSDate date]; // 23/07/2015
// Start calculating next date ->
NSDate *nextDate = /* interval added to past date */
// Is result later than now?
// No? Calculate again
// Abracadabra
NSLog(@"nexDate = %@",nextDate); // 28/07/2015
NSDateComponents *twoWeeksDateComponents = [NSDateComponents new];
twoWeeksDateComponents.weekOfMonth = 2;
NSDate *date = self.picker.date;
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *now = [NSDate date];
NSDate *nextDate = date;
NSComparisonResult result = [nextDate compare:now];
while (result == NSOrderedAscending) {
nextDate = [calendar dateByAddingComponents:kTwoWeeksDateComponents
toDate:nextDate
options:NSCalendarMatchNextTime];
result = [nextDate compare:now];
}
NSLog(@"nexDate = %@",nextDate); // 28/07/2015
您确实可以不用迭代就完成这项工作，而只需使用一点算术。您正在寻找某个因子f严格大于另一个值n的最近倍数。日历计算要复杂一点，但仍然只是算术（当然，所有繁重的工作都由NSCalendar来完成，例如闰年）
从用户处获取您喜欢的重复间隔，并构造一个表示该间隔的
NSDateComponentsNSCalendarUnit repeatUnit = NSCalendarUnitWeekOfYear;
NSUInteger repeatInterval = 2;
NSDateComponents * repeatComps = [NSDateComponents new];
[repeatComps setValue:repeatInterval forComponent:repeatUnit];
NSCalendar * cal = [NSCalendar currentCalendar];
NSDateComponents * deltaComps = [cal components:repeatUnit
fromDate:pastDate
toDate:now
options:0];
NSInteger deltaVal = [deltaComps valueForComponent:repeatUnit];
NSCalendarUnitMonthrepeatUnitNSInteger repeatsJustPastNow = 1 + deltaVal - (deltaVal % repeatInterval);
NSDateComponents * toNowComps = [NSDateComponents new];
[toNowComps setValue:repeatsJustPastNow
forComponent:repeatUnit];
NSDate * nextDate;
nextDate = [cal dateByAddingComponents:toNowComps
toDate:pastDate
options:0];
Jawboxer的。您确实可以不用迭代就完成这项工作，而只需使用一点算术。您正在寻找某个因子f严格大于另一个值n的最近倍数。日历计算要复杂一点，但仍然只是算术（当然，所有繁重的工作都由NSCalendar来完成，例如闰年）
从用户处获取您喜欢的重复间隔，并构造一个表示该间隔的
NSDateComponentsNSCalendarUnit repeatUnit = NSCalendarUnitWeekOfYear;
NSUInteger repeatInterval = 2;
NSDateComponents * repeatComps = [NSDateComponents new];
[repeatComps setValue:repeatInterval forComponent:repeatUnit];
NSCalendar * cal = [NSCalendar currentCalendar];
NSDateComponents * deltaComps = [cal components:repeatUnit
fromDate:pastDate
toDate:now
options:0];
NSInteger deltaVal = [deltaComps valueForComponent:repeatUnit];
NSCalendarUnitMonthrepeatUnitNSInteger repeatsJustPastNow = 1 + deltaVal - (deltaVal % repeatInterval);
NSDateComponents * toNowComps = [NSDateComponents new];
[toNowComps setValue:repeatsJustPastNow
forComponent:repeatUnit];
NSDate * nextDate;
nextDate = [cal dateByAddingComponents:toNowComps
toDate:pastDate
options:0];
Jawboxer's.编辑：正如Josh指出的，这并不能解释闰年。因此，这是一个很好的实现示例，它似乎可以在短期测试中工作，但存在漏洞。它也会在日志中关闭几个小时，因为
dateFromString:编辑：正如乔希指出的，这并不能解释闰年。因此，这是一个很好的实现示例，它似乎可以在短期测试中工作，但存在漏洞。它也会在日志中关闭几个小时，因为
dateFromString:我很早就提出了另一个解决方案
NSDate *date = ...;
static NSTimeInterval k2WeeksInterval = 14 * 24 * 60 * 60.0;
NSTimeInterval timeInterval = -date.timeIntervalSinceNow;
double repeats = ceil(timeInterval / k2WeeksInterval);
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [NSDateComponents new];
components.weekOfYear = repeats * 2;
NSDate *nextDate = [calendar dateByAddingComponents:components
toDate:date
options:NSCalendarMatchNextTime];
我很早就提出了另一个解决方案
NSDate *date = ...;
static NSTimeInterval k2WeeksInterval = 14 * 24 * 60 * 60.0;
NSTimeInterval timeInterval = -date.timeIntervalSinceNow;
double repeats = ceil(timeInterval / k2WeeksInterval);
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [NSDateComponents new];
components.weekOfYear = repeats * 2;
NSDate *nextDate = [calendar dateByAddingComponents:components
toDate:date
options:NSCalendarMatchNextTime];
最后在看到你的之前发布了我的。。。使用我的可以吗（它似乎总是返回正确的日期，保留时间，并以疯狂的间隔工作，如1周+1天+3小时+4分钟）？或者我应该检查日期组件，而不仅仅是计算时间间隔？你的版本不能很容易地处理月或年的重复单位。例如，尝试使用2015-03-01的开始日期和1年的间隔
NSCalendarNSDateComponentspastDaterepeatUnitnowrepeatsToNownextDateNSCalendarNSDateComponentspastDaterepeatUnitnowrepeatsToNownextDate