将 NSString 与星期几和 NSDate 与时间组合成 NSDate 对象

Question

我有以下两个对象： 一个带有星期几的 NSString 对象，即星期一、星期二、星期三等。 使用 UIDatePickerModeTime 从 UIDatePicker 保存的 NSDate 对象。

我需要创建第三个对象 NSDate，它是 NSString 的下一次出现以及 NSDate 中的时间。

//Ex. Tuesday
NSString *confessOn = [[NSUserDefaults standardUserDefaults] objectForKey:kRemindToConfessOn];

//Ex. 2011-02-11 20:13:19
NSDate *confessAt = [[NSUserDefaults standardUserDefaults] objectForKey:kRemindToConfessAt];

NSDate *fireDate = //should be an NSDate with the value 2011-02-15 20:13:19

Answer 1

NSDateFormatter * df = [[[NSDateFormatter alloc] init] autorelease];
[df setLocale:[[[NSLocale alloc] initWithLocaleIdentifier(@"en")] autorelease];
[df setDateFormat:@"EEEE"];
NSDate *confessOnDate = [df dateFromString:confessOn];
NSCalendar *cal = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDateComponents *confessOnComps = [cal components:NSWeekdayCalendarUnit fromDate:confessOnDate];
NSDateComponents *confessAtComps = [cal components:NSWeekdayCalendarUnit fromDate:confessAt];
NSInteger weekdayDifference = ([confessOnComps weekday] + 7 - [confessAtComps weekday]) % 7;
NSDate *fireDate = [confessAt dateByAddingTimeInterval:weekdayDifference * 86400];