ios - 如何计算给定日期后剩余的天，时，分和秒？

Question

在我的应用程序中，我需要从JSON响应中获取给定日期的天，小时，分钟和秒。以下是我得到的日期和时间:

"date_time" = "2017-01-31 08:30:00";

并需要计算剩余天数:6小时:18分钟:24秒:30

结束日期将是今天的日期。我尝试了下面的代码，但它给了我很多天(我认为这需要UTC时区)，并且还在SO上尝试了许多答案。

NSString *start = [[self.eventsArray valueForKey:@"date_time"]objectAtIndex:0];


NSDateFormatter *date = [[NSDateFormatter alloc] init];
[date setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSString *end = [date stringFromDate:[NSDate date]];


NSDateFormatter *f = [[NSDateFormatter alloc] init];
[f setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *startDate = [f dateFromString:start];
NSDate *endDate = [f dateFromString:end];


NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSDateComponents *components = [gregorianCalendar components:NSCalendarUnitDay
                                                    fromDate:startDate
                                                      toDate:endDate
                                                     options:0];
NSLog(@"day : %ld H: %ld M : %ld S:%ld", [components day], (long)[components hour],(long)[components minute],(long)[components second]);

请有人帮我卡住。

Answer 1

您在这里输入错误，您的fromDate应该是今天的日期，即[NSDate date]，而toDate将是您的startDate。因此，您的代码应该是这样的。

NSString *end = [[self.eventsArray valueForKey:@"date_time"]objectAtIndex:0];

NSDateFormatter *date = [[NSDateFormatter alloc] init];
[date setDateFormat:@"yyyy-MM-dd HH:mm:ss"];    

NSDateFormatter *f = [[NSDateFormatter alloc] init];
[f setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
//Start date
NSDate *startDate = [NSDate date];
NSDate *endDate = [f dateFromString:end];


NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSDateComponents *components = [gregorianCalendar components:NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond
                                                    fromDate:startDate
                                                      toDate:endDate
                                                     options:0];
NSLog(@"day : %ld H: %ld M : %ld S:%ld", [components day], (long)[components hour],(long)[components minute],(long)[components second]);