Question

I use the following regular expression:

NSString *reg1 = @"/[$|§|%|&|{|}|'|`|´|^|°|~]/i";

NSPredicate *messageTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",
                           reg1];

And I test if the string matches this regex:

if([messageTest evaluateWithObject:message] == NO){
        messageValid = NO;
        NSLog(@"message invalid");
}

So if the text contains any of the characters that are specified in the regular expression the text is invalid.

This regex worked for me in javascript. However in objective-c I get always NO regardless of what characters are in the string.

Where is the problem?

Answer 1

There are essentially two problems with your code. Firstly, your regular expression

NSString *reg1 = @"/[$|§|%|&|{|}|'|`|´|^|°|~]/i";

is wrong:

• ICU regular expressions do not use /pattern/modifier. Also, why would you specify a case-insensitive match for that character set?
• ICU regular expressions need the following characters to be quoted: $ { } ^
• As ridgerunner mentioned, do not use | to separate characters in a character class.

The ICU regular expression you want is

[\$§%&\{\}'`´\^°~]

Try this in your program:

NSString *reg1 = @"[\\$§%&\\{\\}'`´\\^°~]";

(note that the \ character is represented as \\ in an Objective-C string.)

Secondly, you’re testing

if([messageTest evaluateWithObject:message] == NO)

to check whether a message is invalid. But -evaluateWithObject: returning NO means that there wasn’t a match, hence the string doesn’t contain any of those characters, hence the string is valid. You need to change that to its opposite, namely:

if([messageTest evaluateWithObject:message])

which means that there was a match, hence the string contain at least one of those characters, hence the string isn’t valid.