3
给定NSDate
和NSCalendar
,如何确定指定日期之后当天的小时数。取决于下一天是进入夏令时(23),正常(24)还是现在的夏令时(25),这将是23,24或25。确定给定日期(加或减DST班次小时数)的小时数
给定NSDate
和NSCalendar
,如何确定指定日期之后当天的小时数。取决于下一天是进入夏令时(23),正常(24)还是现在的夏令时(25),这将是23,24或25。确定给定日期(加或减DST班次小时数)的小时数
你可以问日历中的任意单元有多长(和单位开始时)与rangeOfUnit:startDate:interval:forDate:
。
// Test date (the day DST begins)
NSDateComponents *components = [[NSDateComponents alloc] init];
components.year = 2012;
components.month = 3;
components.day = 11;
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *date = [calendar dateFromComponents:components];
NSTimeInterval dayLength;
[calendar rangeOfUnit:NSDayCalendarUnit startDate:NULL interval:&dayLength forDate:date];
NSLog(@"%f seconds", dayLength);
注意rangeOfUnit:...
可以techincally失败并返回NO
,但如果控制不应该是能够发生的输入。
// Test input
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.dateFormat = @"yyyy MM dd HH:mm:ss";
NSDate *referenceDate = [formatter dateFromString:@"2012 03 24 13:14:14"];
// Get reference date with day precision
NSCalendar *calendar = [NSCalendar currentCalendar];
unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;
NSDateComponents *components = [calendar components:unitFlags fromDate:referenceDate];
NSDate *today = [calendar dateFromComponents:components];
// Set components to add 1 day
components = [[NSDateComponents alloc] init];
components.day = 1;
// The day after the reference date
NSDate *tomorrow = [calendar dateByAddingComponents:components toDate:today options:0];
// The day after that
NSDate *afterTomorrow = [calendar dateByAddingComponents:components toDate:tomorrow options:0];
// Difference in hours: 23, 24 or 25
NSUInteger hours = [afterTomorrow timeIntervalSinceDate:tomorrow]/3600;
看一看[“确定时域的区别”(https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/DatesAndTimes/Articles/dtCalendricalCalculations.html#//apple_ref/doc/uid/TP40007836-SW8)的日期和时间编程指南。 – 2012-02-24 19:32:28