Common usage of iOS Study Notes 25-NSDate (1)

 

1. The following methods can be used to create or Initialize an instance:

The class methods used to create an NSDate instance include:

+ (Id) date;

Returns the current time.

 

+ (Id) dateWithTimeIntervalSinceNow :( NSTimeInterval) secs;

The return value is based on the current time, and the time after secs seconds is passed.

 

+ (Id) dateWithTimeIntervalSinceReferenceDate :( NSTimeInterval) secs;

The returned time is based on 2001/01/01 GMT, and the time passed by secs seconds.

 

+ (Id) dateWithTimeIntervalSince1970 :( NSTimeInterval) secs;

The return value is based on GMT, and the time after secs seconds is passed.

 

+ (Id) distantFuture;

Returns the day of the future many years later.

For example, if you need a time value that is later than the current time (Now), you can call this method. The test returns 4000/12/31 16:00:00

 

+ (Id) distantPast;

Returns a day many years ago.

For example, if you need a time value that is earlier (smaller) than the current time, you can call this method. Test returned 0001/12/31 17:00:00 BC

 

The method used to create an NSDate instance is

-(Id) addTimeInterval :( NSTimeInterval) secs;

The returned result is based on the time saved in the current instance, and the time passed by secs seconds

 

The methods used to initialize an NSDate instance include:

-(Id) init;

Initialize to the current time. Similar to the date Method

 

-(Id) initWithTimeIntervalSinceReferenceDate :( NSTimeInterval) secs;

The initialization is based on 2001/01/01 GMT, and the time after secs seconds is passed. Similar to dateWithTimeIntervalSinceReferenceDate: Method

 

-(Id) initWithTimeInterval :( NSTimeInterval) secs sinceDate :( NSDate *) refDate;

Initialized to refDate as the benchmark, and then the time passed by secs seconds

 

-(Id) initWithTimeIntervalSinceNow :( NSTimeInterval) secs;

The initialization is based on the current time, and the time after secs seconds is passed.

 

 

2. The following methods are available for comparison between dates:

-(BOOL) is1_todate :( NSDate *) otherDate;

YES is returned for comparison with otherDate.

 

-(NSDate *) earlierDate :( NSDate *) anotherDate;

Returns the date earlier than anotherDate.

 

-(NSDate *) laterDate :( NSDate *) anotherDate;

Returns the date later than anotherDate.

 

-(NSComparisonResult) compare :( NSDate *) other;

This method is called for sorting:

. NSOrderedSame is returned when the date value saved by the instance and anotherDate are the same.

. NSOrderedDescending is returned when the date value saved by the instance is later than anotherDate.

. NSOrderedAscending is returned when the date value saved by the instance is earlier than anotherDate.

 

 

3. The interval for retrieving data can be as follows:

-(NSTimeInterval) timeIntervalSinceDate :( NSDate *) refDate;

Returns the time interval between the Instance Storage Time and refDate Based on refDate.

 

-(NSTimeInterval) timeIntervalSinceNow;

Returns the time interval between the Instance Storage Time and the current time (Now) based on the current time (Now ).

 

-(NSTimeInterval) timeIntervalSince1970;

Return the time interval between the Instance Storage Time and GMT based on January 1, GMT.

 

-(NSTimeInterval) timeIntervalSinceReferenceDate;

Returns the time interval between the Instance Storage Time and the GMT value of 2001/01/01.

 

 

+ (NSTimeInterval) timeIntervalSinceReferenceDate;

Returns the interval between the current time (Now) and 2001/01/01 GMT Based on the GMT value of 2001/01/01.

 

 

4. Represent the time as a string

-(NSString *) description;

Time is represented in the format of YYYY-MM-DD HH: MM: SS ± HHMM.

"± HHMM" indicates the number of hours and minutes of time zone difference with GMT. For example, if the time zone is set to Beijing, "± HHMM" is displayed as "+ 0800"