ios - 从今天的日期和带有时间的字符串构造一个 NSDate

Question

如果我有一个表示时间的字符串，比如“10:45 am”，然后执行以下操作来解析该字符串:

NSDateFormatter *dateFormat;
dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:@"h:mm a"];
NSLog(@"%@", [dateFormat dateFromString:@"10:45 AM"]);

我会记录这个:

2013-09-09 17:52:30.416 TimeTest[49491:a0b] 2000-01-01 15:45:00 +0000

如何在给定时间为当天创建一个 NSDate？我试过了

NSDate *date = [NSDate date];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"h:mm a"];
NSDate *time = [formatter dateFromString:@"10:45 AM"];
NSDateComponents *timeComponents = [[NSCalendar currentCalendar] components:(NSHourCalendarUnit | NSMinuteCalendarUnit ) fromDate:time];
NSDateComponents *dateComponents = [[NSCalendar currentCalendar] components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:date];
NSDateComponents *newComponents = [[NSDateComponents alloc]init];
newComponents.timeZone = [NSTimeZone systemTimeZone];
[newComponents setDay:[dateComponents year]];
[newComponents setMonth:[dateComponents month]];
[newComponents setYear:[dateComponents year]];
[newComponents setHour:[timeComponents hour]];
[newComponents setMinute:[timeComponents minute]];
NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *combinedDate = [gregorianCalendar dateFromComponents:newComponents];
NSLog(@"%@", combinedDate);

结果

2013-09-09 19:57:14.506 TimeTest[49712:a0b] 2019-03-06 15:45:00 +0000

我该怎么办？

Answer 1

我不太确定你在找什么。据我了解，您想用当前的年、月和日构建一个日期，但要通过从字符串中解析提供的时间来构建日期。如果是这种情况，正如其他人所指出的那样，您需要使用 NSDateComponents。

我根据您的代码编写了这些行。他们应该通过合并两个日期来构建一个日期。当前一个和你解析的那个。

// Get the full current date
NSDate *date = [NSDate date];

// Get the current calendar
NSCalendar *calendar = [NSCalendar currentCalendar];

// Split the date into components but only take the year, month and day and leave the rest behind
NSDateComponents *dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:date];

// Build the date formatter
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"h:mm a"];

// Convert the string time into an NSDate
NSDate *time = [formatter dateFromString:@"10:45 AM"];

// Split this one in components as well but take the time part this time
NSDateComponents *timeComponents = [[NSCalendar currentCalendar] components:(NSHourCalendarUnit | NSMinuteCalendarUnit ) fromDate:time];

// Do some merging between the two date components
dateComponents.hour = timeComponents.hour;
dateComponents.minute = timeComponents.minute;

// Extract the NSDate object again
NSDate *result = [calendar dateFromComponents:dateComponents];

// Check if this was what you where looking for
NSLog(@"%@",result);

请注意，此示例代码目前尚未优化。有更清晰的方法可以通过使用时间间隔来获取您正在寻找的内容，但我觉得您想要一个关于如何复制和粘贴组件然后提取日期的肮脏的简单示例。