Manipulate string in objective-c to remove substring between 2 characters - objective-c

Question

I want to parse a date string that I receive from a web service. However, I sometimes receive the date with decimal component and sometimes without decimal component. Also, sometimes the date comes with a different number of decimal digits.
Assume you got the following date:
NSString *dateString = #"2013-07-22T220713.9911317-0400";
How can remove the decimal values? I want to end up with:
#"2013-07-22T220713-0400";
So I can process it with the DateFormatter that uses no decimal.

Answer 1

You could use a regular expression to match the first occurrence of a decimal followed by numbers, and remove them:
NSString *dateString = #"2013-07-22T220713.9911317-0400";
NSRegularExpression * regExp = [NSRegularExpression regularExpressionWithPattern:#"\\.[0-9]*" options:kNilOptions error:nil];
dateString = [dateString stringByReplacingCharactersInRange:[regExp rangeOfFirstMatchInString:dateString options:kNilOptions range:(NSRange){0, dateString.length}] withString:#""];

Answer 2

Based on #JeffCompton 's suggestion I ended up doing this:
+ (NSDate *)dateFromISO8601:(NSString *)dateString {
if (!dateString) return nil;
if ([dateString hasSuffix:#"Z"]) {
dateString = [[dateString substringToIndex:(dateString.length - 1)] stringByAppendingString:#"-0000"];
}
NSString *cleanDateString = dateString;
NSArray *dateComponents = [dateString componentsSeparatedByCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:#"."]];
if ([dateComponents count] > 1){
NSArray *timezoneComponents = [[dateComponents objectAtIndex:1] componentsSeparatedByCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:#"-"]];
if ([timezoneComponents count] > 1){
cleanDateString = [NSString stringWithFormat:#"%#-%#", [dateComponents objectAtIndex:0], [timezoneComponents objectAtIndex:1]];
}
}
dateString = [cleanDateString stringByReplacingOccurrencesOfString:#":" withString:#""];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat = #"yyyy-MM-d'T'HHmmssZZZ";
NSDate *resultDate = [dateFormatter dateFromString:dateString];
return resultDate;
}
This is a modification of some open-source code but I lost the reference to the original code.
The reason for all the modifications is that I am connecting to API's that can give me the date with decimals or without, and sometimes without the : separating HH, mm, and ss.