我怎么能得到一个NSDate对象的年/月/日，没有其他信息?我意识到我可以用类似这样的东西来做这件事:
NSCalendar *cal = [[NSCalendar alloc] init];
NSDateComponents *components = [cal components:0 fromDate:date];
int year = [components year];
int month = [components month];
int day = [components day];
但是对于像获取NSDate的年/月/日这样简单的事情来说，这似乎是一大堆麻烦。还有其他解决办法吗?
当前回答
如果你想从NSDate中获得单个的NSDateComponents，你肯定需要Itai Ferber建议的解决方案。但如果你想直接从NSDate到NSString，你可以使用NSDateFormatter。
其他回答
NSDate *currDate = [NSDate date];
NSCalendar* calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents* components = [calendar components:NSDayCalendarUnit|NSMonthCalendarUnit|NSYearCalendarUnit fromDate:currDate];
NSInteger day = [components day];
NSInteger month = [components month];
NSInteger year = [components year];
NSLog(@"%d/%d/%d", day, month, year);
试试下面的方法:
NSString *birthday = @"06/15/1977";
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"MM/dd/yyyy"];
NSDate *date = [formatter dateFromString:birthday];
if(date!=nil) {
NSInteger age = [date timeIntervalSinceNow]/31556926;
NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:date];
NSInteger day = [components day];
NSInteger month = [components month];
NSInteger year = [components year];
NSLog(@"Day:%d Month:%d Year:%d Age:%d",day,month,year,age);
}
[formatter release];
只是重新描述一下Itai的优秀(并且工作!)代码，下面是一个示例助手类，它返回给定NSDate变量的年份值。
如您所见，修改这段代码以获得月或日是很容易的。
+(int)getYear:(NSDate*)date
{
NSDateComponents *components = [[NSCalendar currentCalendar] components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit fromDate:date];
int year = [components year];
int month = [components month];
int day = [components day];
return year;
}
(我真不敢相信，在2013年，我们还得自己编写这样的基本iOS日期函数……)
还有一件事:永远不要使用<和>来比较两个NSDate值。
XCode很乐意接受这样的代码(没有任何错误或警告)，但其结果是一个彩票。你必须使用"compare"函数来比较nsdate:
if ([date1 compare:date2] == NSOrderedDescending) {
// date1 is greater than date2
}
你可以使用NSDateFormatter获取NSDate的独立组件:
NSDateFormatter *df = [[NSDateFormatter alloc] init];
[df setDateFormat:@"dd"];
myDayString = [df stringFromDate:[NSDate date]];
[df setDateFormat:@"MMM"];
myMonthString = [df stringFromDate:[NSDate date]];
[df setDateFormat:@"yy"];
myYearString = [df stringFromDate:[NSDate date]];
如果你想要得到月份的数字而不是缩写，请使用“MM”。如果你想获取整数，使用[myDayString intValue];
我这样做....
NSDate * mydate = [NSDate date];
NSCalendar * mycalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSCalendarUnit units = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
NSDateComponents * myComponents = [mycalendar components:units fromDate:mydate];
NSLog(@"%d-%d-%d",myComponents.day,myComponents.month,myComponents.year);
