Cocoa에서 현재 날짜를 얻는 방법

Cocoa에서 현재 날짜를 얻는 방법

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저는 iPhone 용으로 개발을 시작하고 있으므로 온라인에서 다양한 튜토리얼을보고 있으며 다른 작업을 직접 시도하고 있습니다. 현재 자정까지 카운트 다운을 만들려고합니다. 시, 분, 초의 수를 얻기 위해 다음을 수행합니다 (어딘가에서 찾았습니다).

NSDate* now = [NSDate date];

int hour = 23 - [[now dateWithCalendarFormat:nil timeZone:nil] hourOfDay];
int min = 59 - [[now dateWithCalendarFormat:nil timeZone:nil] minuteOfHour];
int sec = 59 - [[now dateWithCalendarFormat:nil timeZone:nil] secondOfMinute];
countdownLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hour, min,sec];

그러나 내가 사용하는 각 장소 -dateWithCalendarFormat:timeZone:에서 다음과 같은 오류가 발생합니다.

warning: 'NSDate' may not respond to '-dateWithCalendarFormat:timeZone:'
(Messages without a matching method signature will be assumed to return 'id' and accept '...' as arguments.)
warning: no '-hourOfDay' method found
error: invalid operands to binary - (have 'int' and 'id')

이것은 매우 간단한 것 같습니다. 내가 무엇을 놓치고 있습니까?

또한 다른 장소와 다른 시간에 별표 (*)가 시간 바로 뒤 NSDate* now또는 변수 바로 앞에있는 것을 알아 차 렸습니다 NSDate *now. 둘의 차이점은 무엇이며 왜 하나와 다른 하나를 사용합니까?

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다음을 사용해야합니다.

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *dateComponents = [gregorian components:(NSHourCalendarUnit  | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:yourDateHere];
NSInteger hour = [dateComponents hour];
NSInteger minute = [dateComponents minute];
NSInteger second = [dateComponents second];
[gregorian release];

NSDate * now와 NSDate * now 사이에는 차이가 없습니다. 단지 선호도의 문제입니다. 컴파일러 관점에서 보면 아무것도 바뀌지 않습니다.

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iOS 4.2에 문제가 있습니까? 이 코드 사용 :

NSDate *currDate = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
[dateFormatter setDateFormat:@"dd.MM.YY HH:mm:ss"];
NSString *dateString = [dateFormatter stringFromDate:currDate];
NSLog(@"%@",dateString);

-> 20.01.2011 10:36:02

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다음을 사용할 수도 있습니다.

CFGregorianDate currentDate = CFAbsoluteTimeGetGregorianDate(CFAbsoluteTimeGetCurrent(), CFTimeZoneCopySystem());
countdownLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02.0f", currentDate.hour, currentDate.minute, currentDate.second];
CFRelease(currentDate); // Don't forget this! VERY important

나는 이것이 다음과 같은 장점이 있다고 생각합니다.

2. 직접 메모리 할당이 없습니다.
3. 초는 정수 대신 double입니다.
4. 메시지 전화가 없습니다.
5. 더 빨리.

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// 다음 코드를 사용하여 현재 날짜 / 시간을 가져올 수 있습니다.

    NSDate* date = [NSDate date];
    NSDateFormatter* formatter = [[NSDateFormatter alloc] init];
    NSTimeZone *destinationTimeZone = [NSTimeZone systemTimeZone];
    formatter.timeZone = destinationTimeZone;
    [formatter setDateStyle:NSDateFormatterLongStyle];
    [formatter setDateFormat:@"MM/dd/yyyy hh:mma"];
    NSString* dateString = [formatter stringFromDate:date];

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이것을 교체하십시오 :

NSDate* now = [NSDate date];
int hour = 23 - [[now dateWithCalendarFormat:nil timeZone:nil] hourOfDay];
int min = 59 - [[now dateWithCalendarFormat:nil timeZone:nil] minuteOfHour];
int sec = 59 - [[now dateWithCalendarFormat:nil timeZone:nil] secondOfMinute];
countdownLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hour, min,sec];

이것으로 :

NSDate* now = [NSDate date];
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *dateComponents = [gregorian components:(NSHourCalendarUnit  | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:now];
NSInteger hour = [dateComponents hour];
NSInteger minute = [dateComponents minute];
NSInteger second = [dateComponents second];
[gregorian release];
countdownLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hour, minute, second];

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또한 다른 장소와 다른 시간에 별표 ( *)가 시간 바로 뒤 NSDate* now또는 변수 바로 앞에 위치하는 것을 발견했습니다 NSDate *now. 둘의 차이점은 무엇이며 왜 하나와 다른 하나를 사용합니까?

컴파일러는 상관하지 않지만 공백 앞에 별표를 넣으면 오해의 소지가 있습니다. 내 예는 다음과 같습니다.

int* a, b;

What is the type of b?

If you guessed int *, you're wrong. It's just int.

The other way makes this slightly clearer by keeping the * next to the variable it belongs to:

int *a, b;

Of course, there are two ways that are even clearer than that:

int b, *a;

int *a;
int b;

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You need to do something along the lines of the following:

NSDate *now = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:NSHourCalendarUnit fromDate:now];
NSLog(@"%d", [components hour]);

And so on.

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Here's another way:

NSDate *now = [NSDate date];

//maybe not 100% approved, but it works in English.  You could localize if necessary
NSDate *midnight = [NSDate dateWithNaturalLanguageString:@"midnight tomorrow"]; 

//num of seconds between mid and now
NSTimeInterval timeInt = [midnight timeIntervalSinceDate:now];
int hours = (int) timeInt/3600;
int minutes = ((int) timeInt % 3600) / 60;
int seconds = (int) timeInt % 60;

You lose subsecond precision with the cast of the NSTimeInterval to an int, but that shouldn't matter.

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NSDate* now and NSDate *now are the same thing: a pointer to an NSDate object.

You probably want to use descriptionWithCalendarFormat:timeZone:locale: rather than dateWithCalendarFormat: — the latter returns an NSCalendarDate, which the docs say is scheduled to be deprecated at some point.

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Original poster - the way you're determining seconds until midnight won't work on a day when daylight savings starts or ends. Here's a chunk of code which shows how to do it... It'll be in number of seconds (an NSTimeInterval); you can do the division/modulus/etc to get down to whatever you need.

NSDateComponents *dc = [[NSCalendar currentCalendar] components:NSDayCalendarUnit|NSMonthCalendarUnit|NSYearCalendarUnit fromDate:[NSDate date]];
[dc setDay:dc.day + 1];
NSDate *midnightDate = [[NSCalendar currentCalendar] dateFromComponents:dc];
NSLog(@"Now: %@, Tonight Midnight: %@, Hours until midnight: %.1f", [NSDate date], midnightDate, [midnightDate timeIntervalSinceDate:[NSDate date]] / 60.0 / 60.0);

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There is no difference in the location of the asterisk (at in C, which Obj-C is based on, it doesn't matter). It is purely preference (style).

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It took me a while to locate why the sample application works but mine don't.

The library (Foundation.Framework) that the author refer to is the system library (from OS) where the iphone sdk (I am using 3.0) is not support any more.

Therefore the sample application (from about.com, http://www.appsamuck.com/day1.html) works but ours don't.

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CFGregorianDate currentDate = CFAbsoluteTimeGetGregorianDate(CFAbsoluteTimeGetCurrent(), CFTimeZoneCopySystem());
countdownLabel.text = [NSString stringWithFormat:@"%02d:%02d:%2.0f", currentDate.hour, currentDate.minute, currentDate.second];

Mark was right this code is MUCH more efficient to manage dates hours min and secs. But he forgot the @ at the beginning of format string declaration.

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+ (NSString *)displayCurrentTimeWithAMPM 
{
    NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
    [outputFormatter setDateFormat:@"h:mm aa"];

    NSString *dateTime = [NSString stringWithFormat:@"%@",[outputFormatter stringFromDate:[NSDate date]]];

    return dateTime;
}

return 3:33 AM

참고URL : https://stackoverflow.com/questions/1070354/how-do-i-get-the-current-date-in-cocoa