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