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
在Swift 2.0中:
let date = NSDate()
let calendar = NSCalendar(identifier: NSCalendarIdentifierGregorian)!
let components = calendar.components([.Month, .Day], fromDate: date)
let (month, day) = (components.month, components.day)
我写这个答案是因为这是唯一的方法，不给你可选的NSDateComponent变量和/或强制展开这些变量(也适用于Swift 3)。
斯威夫特3
let date = Date()
let cal = Calendar.current
let year = cal.component(.year, from: date)
let month = cal.component(.month, from: date)
let day = cal.component(.day, from: date)
斯威夫特2
let date = NSDate()
let cal = NSCalendar.currentCalendar()
let year = cal.component(.Year, fromDate: date)
let month = cal.component(.Month, fromDate: date)
let day = cal.component(.Day, fromDate: date)
奖金Swift 3有趣的版本
let date = Date()
let component = { (unit) in return Calendar.current().component(unit, from: date) }
let year = component(.year)
let month = component(.month)
let day = component(.day)
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);
从iOS 8.0(和OS X 10)开始，你可以使用component方法来简化获取单个日期组件，如下所示:
int year = [[NSCalendar currentCalendar] component:NSCalendarUnitYear fromDate:[NSDate date]];
应该使事情更简单，希望这是有效地实施。
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];
