Question

Let’s say I have the string:

@"(Mg(Ni+(N(O2)3";

I am wondering if it is possible to replace occurrences of the string “(” but with the exception of “+(“. Thus result;

@"+Mg+Ni+(N+O2)3";

How would I go about doing this?

Answer 1

You can do this sort of more complex string replacements with regular expressions.

You can write the expression using a negative lookbehind to find a ( that is not preceded by a + (though there are simpler alternatives in this case, see @sch’s comment).

Example:

NSString *string = @"(Mg(Ni+(N(O2)3";
NSLog(@"Original string: %@", string);
NSString *pattern = @"(?<!\\+)\\(";
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern options:0 error:NULL];   
NSString *modifiedString = [regex stringByReplacingMatchesInString:string 
                                                           options:0
                                                             range:NSMakeRange(0, [string length])
                                                      withTemplate:@"$1+"];
NSLog(@"After replacement: %@", modifiedString);