Question

i try to extract simple string from string with out success it looks simple but the result alwways as
the string
here is what i have :

-(NSString*) ExtractArtistNameFromString:(NSString*) line
{

    NSString* substringForMatch = @""   
    NSError *error = NULL;
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"\\d+\\s+(.*)"
                                                                        options:NSRegularExpressionCaseInsensitive
                                                                        error:&error];

    if (error) {
        NSLog(@"Error:%@", error);  
    }

    NSArray *matches = [regex matchesInString:line
                                              options:0
                                              range:NSMakeRange(0, [line length])]; 

    NSUInteger elements = [matches count];
    NSLog(@"numberOfMatches:%u",elements);

    if(elements > 0)
    {

        for(NSTextCheckingResult *match in matches)
        {
            NSString* substringForMatch = [line substringWithRange:match.range];
            NSUInteger slen = [substringForMatch length];
            NSLog(@"Extracted  : %@",substringForMatch);
            NSLog(@"%u",slen);
            NSLog(@"%@",substringForMatch);
        }        
    }
    return substringForMatch;
} 

input string is :

1 Barsotti, Marcel

what im trying to extract is the name that is : Barsotti, Marcel

and when i run the app i get this result :

2013-01-29 11:31:24.056 file_parser[2496] numberOfMatches:1
2013-01-29 11:31:24.062 file_parser[2496] Extracted  : 1        Barsotti, Marcel
2013-01-29 11:31:24.064 file_parser[2496] 18
2013-01-29 11:31:24.066 file_parser[2496] 1     Barsotti, Marcel

im using GNUsetup in windows , the make command is:

make CC=clang

Answer 1

I see what you’re trying to do. The documentation for NSTextCheckingResult shows that a result can have multiple ranges within it, yet you’re only referencing the first range.

For example, your RegEx and your string will have 1 match, with 1 capture group within it. These are:

1. 1 Barsotti, Marcel
2. Barsotti, Marcel

Whilst you only have one NSTextCheckingResult, there are multiple ranges within it. You were using

NSString* substringForMatch = [line substringWithRange:match.range];

This will return the first result listed above. What you want is the second. In order to get this, you need to use

NSString* substringForMatch = [line substringWithRange:[match rangeAtIndex:1]];

To make sure you don’t exceed the rangeAtIndex:, the property numberOfRanges exists to allow you to keep within bounds. Remember, [match rangeAtIndex:0] is the same at match.range.