CODEWITHSUNDEEP
objective-ccocoa-touchnsdatensdateformatter
sasquatch
sasquatch

Reputation: 285

Getting an NSDate via NSDateFormatter from a string of unknown format

I know there are many NSDateFormatter questions on here, so if I duplicate, I'm sorry. I just couldn't find anything that was quite what Im asking.

From all the questions here on SO, I have come to the conclusion that -[NSDateFormatter dateFromString:] will always return NULL if your formatter object doesn't have the correct date format. How do you get a date from a string if you don't know the format? I'm trying to get a date from a UITextField.

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setLocale:[NSLocale currentLocale]];
[formatter setLenient:YES];
NSDate *tempDate = [formatter dateFromString:self.birthdayTxtfld.text];
self.currentCustomer.birthday = ([self.birthdayTxtfld.text isEqualToString:@""]) ? NULL : tempDate;
[formatter release];

tempDate is always NULL.

Upvotes: 2

Views: 742

Answers (2)

Jaybit
Jaybit

Reputation: 1864

I think your taking the wrong approach. I would on the other hand restrict and format the UITextField so the user has to enter the date in a specific format. Or just use a date picker. There are just way too may different inputs the user could give you.

Or you can read through this: NSDate

Another option is to create a list of accepted date formats: #define DATEFORMATS @[@"MM/dd/yyyy", @"MM/dd/yy",... Then Have a method that you pass the date string to and check if you can format it:

+ (NSDateFormatter*)getDateFormat:(NSString*)dateString {

    NSArray *dateFormats = DATEFORMATS;
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    NSDate *date = nil;
    for (NSString *dateFormat in dateFormats) {
        [formatter setDateFormat:dateFormat];
        date = [formatter dateFromString:dateString];
        if (date) {
            return formatter;
        }
    }
    return nil;
}

If you get nil its not a date or its in a format you don't support. Otherwise you will have the correct format you need. You can switch this around to return the date instead of the format. I have it this way because I needed the format not the date for a project.

Upvotes: 3

slf
slf

Reputation: 22767

While I'm in agreement with @Jaybit that you probably need to ditch the text box and use a better input, the answer to this specific question lies in some crafty string parsing. Whenever you are doing string parsing, RegEx is your friend. Web developers end up having to do this crap all the time. This example is in JavaScript, but the RegEx ought to be portable enough that it works in ObjC:

http://www.codingoptimist.com/2009/07/using-javascript-and-regex-to-parse.html

You can do this with RegExKit or NSRegularExpression

Upvotes: 1

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