NSDate的操作

時間與文字

//NSString => NSDate

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *date = [dateFormatter dateFromString:@"2014-01-02 14:16:30"];

NSLog(@"%@", date);

[dateFormatter release];

//NSDate => NSString

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

NSString *strDate = [dateFormatter stringFromDate:[NSDate date]];

NSLog(@"%@", strDate);

[dateFormatter release];

//時間的加減

NSDate * anHourAgo = [now dateByAddingTimeInterval:-60*60];

NSDate * anHourAfter = [now dateByAddingTimeInterval:60*60];

//只取某個時間單位

NSDateComponents *comps = [[NSCalendar currentCalendar] components:NSMonthCalendarUnit | NSDayCalendarUnit | NSWeekdayCalendarUnit | NSHourCalendarUnit fromDate:record.sleepDate];

index = comps.hour - startComps.hour;

//取得時間差

NSTimeInterVal duration = [now timeIntervalSinceDate:lastTime];

//時間的比較

if ([date compare:previousDate] == NSOrderedAscending) {

    //TODO:date 比 previousDate 來的小

}

if ([date compare:previousDate] == NSOrderedSame) {

    //TODO:date 跟 previousDate 是相同時間

}

if ([date compare:previousDate] == NSOrderedDescending) {

    //TODO:date 比 previousDate 來的大

}

//Sample codes

    date = [NSDate date];

    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];

    formatter.dateFormat = @"YYYY-MM-dd";

    formatter.timeZone = [NSTimeZone defaultTimeZone];

    NSMutableString *dateStr = [NSMutableString stringWithString:[formatter stringFromDate:date]];

    NSDateComponents *comps = [[NSCalendar currentCalendar] components:NSHourCalendarUnit | NSMinuteCalendarUnit fromDate:se.wakeUpDate];

    [dateStr appendFormat:@" %02d:%02d:00", comps.hour, comps.minute];

    formatter.dateFormat = @"YYYY-MM-dd HH:mm:ss";