hi i want to know how to get current date?
i want to compare current date with a date i m fetching from a plist files using following code.
NSDate *expDate = [licenseDictionary objectForKey:#"Expires"];
for comparison i m using the following code
if([curDate compare:expDate] == NSOrderedAscending )
but its not working. can anybody help me.
In the interest of teaching someone how to fish rather than just feeding him:
Have a look at the Date and Time Programming Guide.. The Programming Guides in the documentation are your first stop when trying to understand a topic. They provide an overview of what can be done and contain useful example code.
These guides also have links to the documentation of the specific classes that are used. In this case there is the NSDate Class Reference which has sections on creating dates and comparing dates.
Edit
To answer you comment about this not working, I think the problem could be that you haven't created the object that you've stored in the dictionary as an NSDate. Again. Have a look at the creating dates documentation. It will be something like
NSDate *expiryDate = [NSDate dateWithNaturalLanguageString:#"31/01/10"];
But this is just an example, there are other ways of setting a date string.
To get the current date, simply use:
NSDate * today = [NSDate date];
To compare to another date:
if ([today compare:expirationDate] == NSOrderedAscending)
{
// today's date is before the expiration date
}
Related
I am having some trouble comparing NSDate as they have a different format.
From one side I have a NSDate who looks like this:
2013-12-05T10:12:00.120Z
And from the other side I have another NSDate that looks this way:
2013-12-01 10:1200 +00000
My question is, how could I make the first NSDate look like the 2nd one?
And more important, what does 120Z mean? I guess it's the timezone, but I am not really sure of it.
By the way, is it there any way to can format the NSDate's and updating the time respecting the timezone hour difference?
Thanks a lot!
EDITED:
To get the 1st NSDate I do the following (I need to get the last opened date of a file):
MDItemRef item = MDItemCreate(NULL, (__bridge CFStringRef)filePath);
NSDate *date = (NSDate*)CFBridgingRelease(MDItemCopyAttribute(item,
kMDItemLastUsedDate));
And to get the 2nd NSDate I do the following:
NSDate* threeDaysAgo = [NSDate dateWithTimeIntervalSinceNow:-259200];
Convert both the dateStrings to NSDate and then you can easily compare the dateObjects.
For converting string to date thing you need :
NSDateFormatter
For comparing two dates :
resultant = [dateOne compare:dateTwo]
resultant can be NSOrderedAscending or NSOrderedSame or NSOrderedDescending.
You have a misunderstanding of what an NSDate is. It is not "in a format" at all, but is actually a wrapper around a a double which is the number of seconds since Jan 1st 1970 12:00am UTC. You can compare your two dates directly to see which one is the earlier. However, if you are trying to compare for equality, it's more tricky. If you want to see if they are within one minute of each other, you can do something like
[date1 timeIntervalSinceDate: date2] < 60.0;
currently, i am working on an app that uses Core Data. One of my managed objects has a property that keeps track of the day of week (Sunday - Saturday) as an integer (0-6). For the sake of sorting the objects by day as well as less overhead in saving, i definitely believe the best practice is to save the days as indexes and then convert to string during runtime. The question becomes the best practice to convert the index to its corresponding day as a string. ie. 0=>#"Sunday" and 6 => #"Saturday". I can obviously use NSCalendar and NSDate and NSDateComponents to achieve this. It just seems like a very roundabout way to go about it given the simplicity of the task. Naturally, a simple NSString array defined as such could do the trick:
NSString *dayOfWeek[7] = {#"Sunday",#"Monday",#"Tuesday",#"Wednesday",#"Thursday",#"Friday'"#"Saturday"};
But then i find myself constantly redefining this same variable over and over again. A global constant NSString could work. Another idea I had was creating a function that used this dayOfWeek array and then including it in the files that need it. What do you think. What's the best practice?
How about one of the weekdaySymbols methods of NSDateFormatter?
Another solution would be to define a category method on NSString, for example, to return the string based on the number. Then the strings array can be static and only used in that method.
I am having problem finding date from string that is formatted using NSDateFormatter
Now, I am using this code:
NSDate *afterDate=[NSDate dateWithNaturalLanguageString:balanceDateAfter.stringValue];
This code returning date with GeorgianCalendar format but I want it in PersianCalendar.
I think if I use this code :
NSDate *afterDate=[NSDate dateWithNaturalLanguageString:balanceDateAfter.stringValue locale:];
It will return true date format but I don't know how can I use locale to set appropriate date formatter ( or my system locale ).
balanceDateAfter in above codes is an NSTextfield with NSDateFormatter.
NSDates do not have a calendar. An NSDate represents an absolute moment in time as defined by the difference between that moment and the first instant of 1st January 2001 in GMT. Basically, it's a positive or negative number of seconds, nothing more.
If you have an appropriate formatter assigned to the text field, you should get its value using -objectValue, not -stringValue. That way, you will be given the NSDate directly and you won't need to parse the string yourself.
I'm getting a date from a webservice back in the form MM00yyyy -- it is just the two-digit month, followed by two 0's, and then the four-digit year. When I do this:
NSString *expDate = #"12001975";
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"MM00yyyy"];
NSDate postDate = [dateFormat dateFromString:expDate];
[dateFormat dateFromString] returns nil for some reason. I have also tried MMddyyyy, and MM'0''0'yyyy, with no success either way. I am converting a similar date, except the 0's are actually the day with no problem using the same method.
To get this working, I would just use the following pattern MMHHyyyy. Since you need only the date and not neccessarily the hour, the HH will use the 00 to set the time as zeroth hour and hence you will get the date that you are looking for. Again this is just a hack and a workaround only to solve your current problem.
Have a look at the Date Formatting Guide from Apple. The section "Use Format Strings to Specify Custom Formats" lists all the different standards the are supported by various iOS versions for specifying a format string. I would say that "00" is not allowed, so that is the reason why "MM00yyyy" is failing. Similarly, "MMddyyyy" is also failing because no day can be "00".
I don't know if you can have more luck with UNIX functions, as the Apple doc suggests:
For date and times in a fixed, unlocalized format, that are always guaranteed to use the same calendar, it may sometimes be easier and more efficient to use the standard C library functions strptime_l and strftime_l.
Be aware that the C library also has the idea of a current locale. To guarantee a fixed date format, you should pass NULL as the loc parameter of these routines. This causes them to use the POSIX locale (also known as the C locale), which is equivalent to Cocoa's en_US_POSIX locale, as illustrated in this example.
struct tm sometime;
const char *formatString = "%Y-%m-%d %H:%M:%S %z";
(void) strptime_l("2005-07-01 12:00:00 -0700", formatString, &sometime, NULL);
NSLog(#"NSDate is %#", [NSDate dateWithTimeIntervalSince1970: mktime(&sometime)]);
// Output: NSDate is 2005-07-01 12:00:00 -0700
Getting the format strings right seems much more like art than science. I suggest you make a new string without the 00 in it and then have your DateFromatter process that with "MMyyyy".
While this might not be the "correct" way to do it, it should solve your problem pretty quickly.
The zeros are unsupported symbols. Apple supports the following characters for date formatting: http://unicode.org/reports/tr35/tr35-10.html#Date_Format_Patterns See the day section.
This is a completely noobish question, but I spent 2 hours yesterday trying to make it work, and I'm obviously missing something very basic.
What I need to do is take input from user of date/time and count back 90 minutes for an alert.
Could someone please post an example calculation, where you have a var that holds user input and a new var that receives the result of this computation? (all done in Objective C for use in an iPhone app) Thank you!
I suspect you could do something like:
NSDate *alertDate = [userDate dateByAddingTimeInterval:-5400.0];
I think this should work:
NSDate * alarmDate = [NSDate dateWithTimeInterval:5400 sinceDate:userDefinedDate];
NSDate * now = [NSDate date];
NSTimeInterval wait = [now timeIntervalSinceDate:alarmDate];
[self performSelector:#selector(callAlarm) withObject:nil afterDelay:fabs(wait)];
Although I do agree with Nick too, adding your work its much more productive..
Assuming you have a UIDatePicker, your target date will already be in an NSDate object. If it's coming from another source, you're probably ending up with it in an NSDate object, either from a string via an NSDateFormatter or by some other means.
From an NSDate object, you can get an NSTimeInterval relative to some absolute date. That's a C primitive type (it's a double in practice, but obviously don't code to depend on that) that you can do arithmetic directly on. So you can subtract 90 minutes directly from that. There are then various + dateWithTimeInterval... class methods on NSDate that will allow you to get a date from the result.