Pull string from regex in Objective-C

Question

I have a string 2000-01-01T10:00:00Z I want to pull time time out of that string: 10:00

Can anyone tell me how to do it using NSRegularExpression

I tried the following code but it isn't working (returning no results)

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(\d{2}:\d{2})" options:NSRegularExpressionCaseInsensitive error:NULL];
NSString *newSearchString = [regex firstMatchInString:opening_time options:0 range:NSMakeRange(0, [opening_time length])];

Where opening_time is "2000-01-01T10:00:00Z"

Why are you using regex to parse a date? Use NSSateFormatter instead. — Richard J. Ross III
– Richard J. Ross III, Commented Oct 23, 2012 at 3:33
Because I wasn't sure that the date was valid, and thought that I might run into problems trying to parse invalid dates. — Sean
– Sean, Commented Oct 23, 2012 at 3:49

Sergey Kalinichenko · Accepted Answer · 2012-10-23 03:44:56Z

10

I think you need to double the slashes in front of your \ds:

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(\\d{2}:\\d{2})" options:NSRegularExpressionCaseInsensitive error:NULL];
NSTextCheckingResult *newSearchString = [regex firstMatchInString:opening_time options:0 range:NSMakeRange(0, [opening_time length])];
NSString *substr = [opening_time substringWithRange:newSearchString.range];
NSLog(@"%@", substr);

This prints 10:00

edited Oct 23, 2012 at 3:44

answered Oct 23, 2012 at 3:34

Sergey Kalinichenko

729k85 gold badges1.2k silver badges1.6k bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Matt Long · Accepted Answer · 2012-10-23 05:25:38Z

Use NSDateFormatter. It looks like you're probably getting this date from a Rails web service? Try this:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"YYYY-MM-dd'T'HH:mm:ss'Z'"];

NSDate *date = [dateFormatter dateFromString:opening_time];

NSDateComponents *components = [[NSCalendar currentCalendar] 
                          components:kCFCalendarUnitHour fromDate:date];

NSInteger hour = [components hour]

// Hour should now contain 10 with your sample date

If you want to get any other components, change your components parameter adding the flags for the components you want to extract. Something like this

NSDateComponents *components = [[NSCalendar currentCalendar] 
                          components:kCFCalendarUnitHour | kCFCalendarUnitMinute 
                            fromDate:date];

NSInteger hour = [components hour];
NSInteger minute = [components minute];

rmaddy · Accepted Answer · 2012-10-23 03:49:32Z

0

If all you really want is the 10:00 part of this fixed format string, why not avoid the regular expression and simply get the substring:

NSString *timeStr = [opening_time substringWithRange:NSMakeRange(11, 5)];

Of course you might consider parsing the string into an NSDate using an NSDateFormatter with the specified format. Make sure the date formatter's locale is set to en_US_POSIX since it is fixed format and not user focused.

The approach you take depends on what you will do with the time you extract. If you want to display it to the user then you want to use an NSDateFormatter so you can format it properly for the user's locale.

answered Oct 23, 2012 at 3:49

rmaddy

319k44 gold badges548 silver badges591 bronze badges

Collectives™ on Stack Overflow

Pull string from regex in Objective-C

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related