Objective-C

Regular Expression with Multiple Matches and Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups and multiple matches. Objective-C

#import <CkoStringBuilder.h>
#import <NSString.h>
#import <CkoJsonObject.h>

BOOL success = NO;

CkoStringBuilder *sb = [[CkoStringBuilder alloc] init];
BOOL crlf = YES;
[sb AppendLine: @"Name: John Smith" crlf: crlf];
[sb AppendLine: @"Name: Jack Johnson" crlf: crlf];
[sb AppendLine: @"Name: Mary Adams" crlf: crlf];

NSLog(@"%@",[sb GetAsString]);

// We have the following string:
// Name: John Smith
// Name: Jack Johnson
// Name: Mary Adams

NSString *pattern = @"Name:\\s+(?<first>\\w+)\\s+(?<last>\\w+)";
CkoJsonObject *json = [[CkoJsonObject alloc] init];
json.EmitCompact = NO;

int timeoutMs = 2000;
int numMatches = [[sb RegexMatch: pattern json: json timeoutMs: [NSNumber numberWithInt: timeoutMs]] intValue];
if (numMatches < 0) {
    // Probably an error in the regular expression.
    // Suggestion: Use AI to help create and/or diagnose regular expressions.
    NSLog(@"%@",sb.LastErrorText);
    return;
}

// Examine the matches:
NSLog(@"%@",[json Emit]);

// Here is the JSON showing the matches.
// Important:  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "Name: John Smith",
//           "idx": 0,
//           "len": 16
//         },
//         {
//           "cap": "John",
//           "idx": 6,
//           "len": 4
//         },
//         {
//           "cap": "Smith",
//           "idx": 11,
//           "len": 5
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Name: Jack Johnson",
//           "idx": 18,
//           "len": 18
//         },
//         {
//           "cap": "Jack",
//           "idx": 24,
//           "len": 4
//         },
//         {
//           "cap": "Johnson",
//           "idx": 29,
//           "len": 7
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Name: Mary Adams",
//           "idx": 38,
//           "len": 16
//         },
//         {
//           "cap": "Mary",
//           "idx": 44,
//           "len": 4
//         },
//         {
//           "cap": "Adams",
//           "idx": 49,
//           "len": 5
//         }
//       ]
//     }
//   ]
// }

// The capture group index is obtained by looking up the name in the JSON result.
// For example:

int idx_first = [[json IntOf: @"named.first"] intValue];
int idx_last = [[json IntOf: @"named.last"] intValue];

int i = 0;
int matchCount = [[json SizeOfArray: @"match"] intValue];
while (i < matchCount) {
    NSLog(@"%@%d%@",@"Match ",i + 1,@":");
    json.I = [NSNumber numberWithInt: i];

    json.J = [NSNumber numberWithInt: idx_first];
    NSLog(@"%@%@",@"first: ",[json StringOf: @"match[i].group[j].cap"]);

    json.J = [NSNumber numberWithInt: idx_last];
    NSLog(@"%@%@",@"first: ",[json StringOf: @"match[i].group[j].cap"]);

    NSLog(@"%@",@"");
    i = i + 1;
}

// Output is: 

// Match 1:
// first: John
// first: Smith
// 
// Match 2:
// first: Jack
// first: Johnson
// 
// Match 3:
// first: Mary
// first: Adams