Objective-c Study 10-nsdate and NSDateFormatter

　NSDate

NSDate time class, inherited from NSObject, whose object represents a point in time

    NSDate *date = [NSDate date];    NSLog (@ "date =%@", date);

2015-12-04 19:08:00.624 ocnsdate[2955:309612] date = 2015-12-04 11:08:00 +0000

Printed display is galini time-month-day time: minutes: seconds + Time zone

1. Get a method to create a distance from the current time interval datewithtimeintervalsincenow: (nstimeinterval)

The essence of (Nstimeinterval) is a double data type

    NSDate *date1 = [nsdate datewithtimeintervalsincenow:8*+]; // 8 hours time difference with Galini, get Beijing time     NSLog (@ "date1 =%@", date1);

2015-12-04 19:08:00.625 ocnsdate[2955:309612] Date1 = 2015-12-04 19:08:00 +0000

　

 Exercise 1: Get the current point in time tomorrow nsdate*nextday = [NSDate datewithtimeintervalsincenow: -* -* -+8* -* -]; Exercise 2: Get next year's point of timeNSDate*nextyear = [NSDate datewithtimeintervalsincenow:366* -* -* -+8* -* -]; NSLog (@"%@", nextyear);

2. Calculates the time interval for a given time and the current point in time . Timeintervalsincenow

Nstimeinterval interval = Nextday.timeintervalsincenow;

NSLog (@ "%.2f", interval);

　3. Calculate the time interval for two points of time timeintervalsincedate:

Nstimeinterval Interval2 = [date timeintervalsincedate:nextyear];

NSLog (@ "%.2f", Interval2);

　　 Timestamp concept: A time interval from 1970.1.1, which is in seconds, called a timestamp

　　the method of time stamp: timeIntervalSince1970

Nstimeinterval INTERVAL3 = [date timeIntervalSince1970];

NSLog (@ "%.2f", INTERVAL3);

　　Convert a timestamp to a time object dateWithTimeIntervalSince1970:

NSDate *date2 = [NSDate datewithtimeintervalsince1970:3600];

NSLog (@ "%@", date2);

　　Get Beijing Time datebyaddingtimeinterval:

NSDate *date3 = [date datebyaddingtimeinterval:8*60*60];

NSLog (@ "%@", date3);

　　Exercise 3: A difference between the current time and a fixed time, if the difference in 60 seconds, then the output "just", if the time difference in 60-3,600 seconds, then the output in "xx minutes ago", if within the 3600~24*3600, then the output in "xx hours ago", if the 24* 3,600 seconds to output fixed time

 fixed time nsdate　　*pastdate = [NSDate datewithtimeintervalsincenow:-370]; NSLog (@"%@", pastdate);
　　Current Time NSDate*nowdate =[NSDate Date];    the difference between the fixed time and the current time Nstimeinterval Interval4=[Nowdate timeintervalsincedate:pastdate]; NSLog (@"Time difference is%.2f seconds", INTERVAL4);
    if(Interval4 <= -) {NSLog (@"just"); }Else if(Interval4 <=3600) {NSLog (@"%.f minutes ago", Interval4/ -);
}Else if(Interval4 <= -*3600) {NSLog (@"%.f hours ago", Interval4/3600); }Else if(Interval4 > -*3600) {NSLog (@"%@", pastdate); }

NSDateFormatter

NSDateFormatter date format class, inherited from Nsformatter, is the primary function of converting NSDate objects to a format and outputting them as strings

NSDateFormatter *formartter = [[NSDateFormatter alloc] init];

　　1. Set the letter used in the date format: Y for the year, M for the month, and D for the day H for the M to represent the seconds

    [Formartter Setdateformat:@ "yyyy mm month dd Day hh mm min ss sec "]    ; *date4 = [nsdate datewithtimeintervalsincenow:0];

　　2. Convert the time object to a formatted format stringfromdate:

When formatted, the system automatically adds time intervals from 0 time zones.

    NSString *datestring = [Formartter stringfromdate:date4];    NSLog (@ "%@", datestring);

Exercise: Output DATE4 as @ "2015 11:43 20 sec"

　　Create a Time Format class object init method creation

NSDateFormatter *myformatter = [[NSDateFormatter alloc] init];

　　Specify the output format setdateformat:@ "Specific time format"

[MyFormatter setdateformat:@] yyyy year mm month DD number hh point mm min SS second "];

　　Receive the converted time stringfromdate with a string:

NSString *datestring1 = [MyFormatter stringfromdate:date4];

NSLog (@ "%@", dateString1);

　　Convert a time string to a NSDate object

For example:@"November 24, 2015 11:10 10 seconds"NSDateFormatter*formatter3 =[[NSDateFormatter alloc] init]; [Formatter3 Setdateformat:@"yyyy mm month dd number hh mm min ss sec"];    prepare the time string NSString*datestring3 =@"November 24, 2015 11:10 10 seconds";    use time format objects to format time objects with time strings NSDate*date5 =[Formatter3 Datefromstring:datestring3];
　　the time to turn around will be back to 0 time zones. NSLog (@"%@", Date5);    you need to manually add 8 hours if you want to NSDate*date6 = [Date5 datebyaddingtimeinterval:8* -* -]; NSLog (@"%@", DATE6);

Objective-c Learning article 10-nsdate and NSDateFormatter