objective c - Converting mutliple date format into a single format in iPhone

Question

I generate a PDF from html source code. I read all the text line by line. I need to get all the dates from whole document. I do get all the dates using regular expression. The problem is i need to convert the string which can be in any date format(dd-MM-yyyy or yyyy-mm-dd or dd/mm/yyyy) to a specific date format (dd MMMM yyyy). I am stuck with this. Any help will be great. I need to read the date format string contains. here is my code...

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *fileDocumentDirectorySavePath = [documentsDirectory stringByAppendingPathComponent:@"Sample.txt"];

NSFileManager *fm = [NSFileManager defaultManager];
if (![fm fileExistsAtPath:fileDocumentDirectorySavePath])
    [fm copyItemAtPath:fileBundlePath toPath:fileDocumentDirectorySavePath error:nil];

NSString* fileContents = 
[NSString stringWithContentsOfFile:fileDocumentDirectorySavePath 
                          encoding:NSUTF8StringEncoding error:nil];

// first, separate by new line
NSArray* allLinedStrings = 
[fileContents componentsSeparatedByCharactersInSet:
 [NSCharacterSet newlineCharacterSet]];
NSString* strsInOneLine;
NSArray *DateArray;
// NSString * regularExpression = @"([1-9]|0[1-9]|[12][0-9]|3[01])(st|nd|rd|th) \w* (19|20)\d\d |(\d{2}-\d{2}-\d{4})|(\d{4}-\d{2}-\d{2})|(\d{2}/\d{2}/\d{4})|(\d{4}/\d{2}/\d{2})";

NSString * regularExpression = @"([1-9]|0[1-9]|[12][0-9]|3[01])(st|nd|rd|th) \w* (19|20)\d\d |(\d{2}-\d{2}-\d{4})|(\d{4}-\d{2}-\d{2})|(\d{2}/\d{2}/\d{4})|(\d{4}/\d{2}/\d{2})|((31(?!\ (Feb(ruary)?|Apr(il)?|June?|(Sep(?=\b|t)t?|Nov)(ember)?)))|((30|29)(?!\ Feb(ruary)?))|(29(?=\Feb(ruary)?\ (((1[6-9]|[2-9]\d)(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00)))))|(0?[1-9])|1\d|2[0-8])\ (Jan(uary)?|Feb(ruary)?|Ma(r(ch)?|y)|Apr(il)?|Ju((ly?)|(ne?))|Aug(ust)?|Oct(ober)?|(Sep(?=\b|t)t?|Nov|Dec)(ember)?)\ ((1[6-9]|[2-9]\d)\d{2})";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:regularExpression
                                                                       options:NSRegularExpressionCaseInsensitive
                                                                         error:&error];
NSString *resultString;

for (int i = 0; i < [allLinedStrings count]; i++) {
           strsInOneLine = [allLinedStrings objectAtIndex:i];
    DateArray = [regex matchesInString:strsInOneLine options:0 range:NSMakeRange(0, [strsInOneLine length])];
    for (NSTextCheckingResult* result in DateArray)
    {
        resultString = [strsInOneLine substringWithRange:result.range];
        NSLog(@"RESULT STRING ===== >%@",resultString);

        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
        [dateFormatter setDateFormat:@"dd-MM-yyyy"];
        NSDate *yourDate = [dateFormatter dateFromString:resultString];
        NSLog(@"NEW DATE ====== > %@",yourDate);
        NSString *myDateStr;
        [dateFormatter setDateFormat:@"dd MMMM yyyy"];
        myDateStr = [dateFormatter stringFromDate:yourDate];
        NSLog(@"NEW DATE STRING ====== > %@",myDateStr);


    }

}

Answer 1

There are no direct way to get this. However there is a work around like this which will work in most of the cases. All you have to do is to add all the possible date formatter to the below dateFormatterList.

- (NSString *)dateStringFromString:(NSString *)sourceString destinationFormat:(NSString *)destinationFormat {

    NSString *convertedDateString = nil;
    NSArray *dateFormatterList = [NSArray arrayWithObjects:@"yyyy-MM-dd'T'HH:mm:ss'Z'", @"yyyy-MM-dd'T'HH:mm:ssZ",
                                  @"yyyy-MM-dd'T'HH:mm:ss", @"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'",
                                  @"yyyy-MM-dd'T'HH:mm:ss.SSSZ", @"yyyy-MM-dd HH:mm:ss",
                                  @"MM/dd/yyyy HH:mm:ss", @"MM/dd/yyyy'T'HH:mm:ss.SSS'Z'",
                                  @"MM/dd/yyyy'T'HH:mm:ss.SSSZ", @"MM/dd/yyyy'T'HH:mm:ss.SSS",
                                  @"MM/dd/yyyy'T'HH:mm:ssZ", @"MM/dd/yyyy'T'HH:mm:ss",
                                  @"yyyy:MM:dd HH:mm:ss", @"yyyyMMdd", @"dd-MM-yyyy",
                                  @"dd/MM/yyyy", @"yyyy-MM-dd", @"yyyy/MM/dd",
                                  @"dd MMMM yyyy", @"MMddyyyy", @"MM/dd/yyyy",
                                  @"MM-dd-yyyy", @"d'st' MMMM yyyy",
                                  @"d'nd' MMMM yyyy", @"d'rd' MMMM yyyy",
                                  @"d'th' MMMM yyyy", @"d'st' MMM yyyy",
                                  @"d'nd' MMM yyyy", @"d'rd' MMM yyyy",
                                  @"d'th' MMM yyyy", @"d'st' MMMM",
                                  @"d'nd' MMMM", @"d'rd' MMMM",
                                  @"d'th' MMMM", @"d'st' MMM",
                                  @"d'nd' MMM", @"d'rd' MMM",
                                  @"d'th' MMM", @"MMMM, yyyy",
                                  @"MMMM yyyy", nil];

    //sourceString = @"20/11/2012";
    //destinationFormat  = @"dd MMMM yyyy";

    if (sourceString) {

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

        for (NSString *dateFormatterString in dateFormatterList) {

            [dateFormatter setDateFormat:dateFormatterString];
            NSDate *originalDate = [dateFormatter dateFromString:sourceString];

            if (originalDate) {

                [dateFormatter setDateFormat:destinationFormat];
                convertedDateString = [dateFormatter stringFromDate:originalDate];
                NSLog(@"Converted date String is %@", convertedDateString);
                break;
            }
        }
        [dateFormatter release];
    }

    return convertedDateString;
}

Add this to your class and use it as,

NSLog(@"%@", [self dateStringFromString:@"2nd August 2012" destinationFormat:@"dd-MM-yyyy"]);

Output: 02-08-2012