时间运算之Calendars

Creating a Calendar

 

 

1：You create a calendar object by specifying an identifier for the calendar you want. Mac OS X provides data for several different calendars—Buddhist, Chinese, Gregorian, Hebrew, Islamic, and Japanese—specified by constants in NSLocale.

 

 

NSCalendar *japaneseCalendar = [[NSCalendar alloc]
        initWithCalendarIdentifier:NSJapaneseCalendar];

 

 

2：You can get the calendar for the user's preferred locale (or in general from any NSLocale object) using the key NSLocaleCalendar,

 

NSCalendar *usersCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:
        [[NSLocale currentLocale] objectForKey:NSLocaleCalendar]];

 

 

3：or most easily using the NSCalendar method currentCalendar. 

 

 

NSCalendar *currentCalendar = [NSCalendar currentCalendar];

 

 

 
Calendrical Calculations

 

取得时间差

 

NSDate *startDate = ...;
NSDate *endDate = ...;
 
NSCalendar *gregorian = [[NSCalendar alloc]
        initWithCalendarIdentifier:NSGregorianCalendar];
 
unsigned int unitFlags = NSMonthCalendarUnit | NSDayCalendarUnit;
 
NSDateComponents *components = [gregorian components:unitFlags
                                          fromDate:startDate
                                          toDate:endDate options:0];
int months = [components month];
int days = [components day];

 

 

api：

 

 

1：从NSDate 中取得NSDateComponents 对象

 

Returns a NSDateComponents object containing a given date decomposed into specified components.

- (NSDateComponents *)components:(NSUInteger)unitFlags fromDate:(NSDate *)date

 

unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
NSDate *date = [NSDate date];
NSDateComponents *comps = [gregorian components:unitFlags fromDate:date];

 

 

2：取得时间差

Returns, as an NSDateComponents object using specified components, the difference between two supplied dates.

- (NSDateComponents *)components:(NSUInteger)unitFlags fromDate:(NSDate *)startingDate toDate:(NSDate *)resultDate options:(NSUInteger)opts

 

NSDate *startDate = ...;
NSDate *endDate = ...;
unsigned int unitFlags = NSMonthCalendarUnit | NSDayCalendarUnit;
NSDateComponents *comps = [gregorian components:unitFlags fromDate:startDate  toDate:endDate  options:0];
int months = [comps month];
int days = [comps day];

 

3：在给定的NSDate 上增加几天，几年等。。。。

 

Returns a new NSDate object representing the absolute time calculated by adding given components to a given date.

- (NSDate *)dateByAddingComponents:(NSDateComponents *)comps toDate:(NSDate *)date options:(NSUInteger)opts

 

NSDate *currentDate = [NSDate date];
NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setMonth:2];
[comps setDay:3];
NSDate *date = [gregorian dateByAddingComponents:comps toDate:currentDate  options:0];
[comps release];

 

4：取得一个指定的时间

Returns a new NSDate object representing the absolute time calculated from given components.

- (NSDate *)dateFromComponents:(NSDateComponents *)comps

 

NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setYear:1965];
[comps setMonth:1];
[comps setDay:6];
[comps setHour:14];
[comps setMinute:10];
[comps setSecond:0];
NSDate *date = [gregorian dateFromComponents:comps];
[comps release];

 

 

 Calendar Units
Specify calendrical units such as day and month.

 

enum {
   NSEraCalendarUnit = kCFCalendarUnitEra,
   NSYearCalendarUnit = kCFCalendarUnitYear,
   NSMonthCalendarUnit = kCFCalendarUnitMonth,
   NSDayCalendarUnit = kCFCalendarUnitDay,
   NSHourCalendarUnit = kCFCalendarUnitHour,
   NSMinuteCalendarUnit = kCFCalendarUnitMinute,
   NSSecondCalendarUnit = kCFCalendarUnitSecond,
   NSWeekCalendarUnit = kCFCalendarUnitWeek,
   NSWeekdayCalendarUnit = kCFCalendarUnitWeekday,
   NSWeekdayOrdinalCalendarUnit = kCFCalendarUnitWeekdayOrdinal
};