How to check if string matches a regular expression in objective-c?

Question

since regular exressions are not supported in Cocoa I find RegexKitLite very usefull. But all examples extract matching strings.

I just want to test if a string matches a regular expression and get a Yes or No.

How can I do that?

Regular expressions 'not supported in Cocoa'? NSRegularExpression has been part of the framework since the release of iOS 4.0, almost a year before this question was asked, and there have apparently been methods that made use of regexes since before NSRegularExpression was introduced, as touched upon in, for instance, Vaz's answer. — Mark Amery
– Mark Amery, Commented Aug 14, 2013 at 16:42

Vladimir · Accepted Answer · 2011-04-25 09:28:13Z

59

I've used NSPredicate for that purpose:

NSString *someRegexp = ...; 
NSPredicate *myTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", someRegexp]; 

if ([myTest evaluateWithObject: testString]){
//Matches
}

answered Apr 25, 2011 at 9:28

Vladimir

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4 Comments

DarkLeafyGreen Over a year ago

thanks, can I use default regular expression syntax for someRegexp?

Vladimir Over a year ago

I think yes, e.g. I used that for simple email validation: NSString *emailRegex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";

Winny Over a year ago

@Vladimir that email regex is inadequate. Email addresses may contain unicode and top level domains are not 2 to 4 characters long.

Vladimir Over a year ago

It served my purpose and I had no complaints from users :) But you can easily replace it with better one, as it is not part of this question anyway

ndmeiri · Accepted Answer · 2019-12-22 01:27:36Z

28

Another way to do this, which is a bit simpler than using NSPredicate, is an almost undocumented option to NSString's -rangeOfString:options: method:

NSRange range = [string rangeOfString:@"^\\w+$" options:NSRegularExpressionSearch];
BOOL matches = range.location != NSNotFound;

I say "almost undocumented", because the method itself doesn't list the option as available, but if you happen upon the documentation for the Search and Comparison operators and find NSRegularExpressionSearch you'll see that it's a valid option for the -rangeOfString... methods since OS X 10.7 and iOS 3.2.

edited Dec 22, 2019 at 1:27

ndmeiri

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answered Feb 17, 2013 at 0:59

Vaz

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Comments

Peter DeWeese · Accepted Answer · 2011-05-27 22:18:28Z

3

NSRegularExpression is another option:

http://developer.apple.com/library/ios/#documentation/Foundation/Reference/NSRegularExpression_Class/Reference/Reference.html

answered May 27, 2011 at 22:18

Peter DeWeese

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Comments

johne · Accepted Answer · 2011-05-28 06:33:57Z

2

Use the -isMatchedByRegex: method.

if([someString isMatchedByRegex:@"^[0-9a-fA-F]+:"] == YES) { NSLog(@"Matched!\n"); }

answered May 28, 2011 at 6:33

johne

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4 Comments

Fattie Over a year ago

NB that is not part of cocoa. very simple answer here .. stackoverflow.com/questions/4353834/…

meaning-matters Over a year ago

Well, @Vladimir's answer seems more simple to me.

chubao Over a year ago

== YES is redundant

Kevin Stewart Over a year ago

Not a great idea to use this library just to perform a very simple action included in Cocoa.

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