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
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
}
其他回答
iOS 8新增功能
ObjC
NSDate *date = [NSDate date];
NSInteger era, year, month, day;
[[NSCalendar currentCalendar] getEra:&era year:&year month:&month day:&day fromDate:date];
斯威夫特
let date = NSDate.init()
var era = 0, year = 0, month = 0, day = 0
NSCalendar.currentCalendar().getEra(&era, year:&year, month:&month, day:&day, fromDate: date)
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];
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);
如果你的目标是iOS 8+，你可以使用新的NSCalendar方便方法以更简洁的格式实现这一点。
首先创建一个NSCalendar并使用所需的NSDate。
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *date = [NSDate date];
你可以通过component:fromDate单独提取组件:
NSInteger year = [calendar component:NSCalendarUnitYear fromDate:date];
NSInteger month = [calendar component:NSCalendarUnitMonth fromDate:date];
NSInteger day = [calendar component:NSCalendarUnitDay fromDate:date];
或者，更简洁地，通过getEra使用NSInteger指针:year:month:day:fromDate:
NSInteger year, month, day;
[calendar getEra:nil year:&year month:&month day:&day fromDate:date];
要了解更多信息和示例，请查看iOS 8中简化的NSDate操作。免责声明，这是我写的文章。
下面是Swift的解决方案:
let todayDate = NSDate()
let calendar = NSCalendar(identifier: NSCalendarIdentifierGregorian)!
// Use a mask to extract the required components. Extract only the required components, since it'll be expensive to compute all available values.
let components = calendar.components(.CalendarUnitYear | .CalendarUnitMonth | .CalendarUnitDay, fromDate: todayDate)
var (year, month, date) = (components.year, components.month, components.day)
