C++

Regular Expression with Multiple Matches and Named Capture Groups

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

#include <CkStringBuilder.h>
#include <CkJsonObject.h>

void ChilkatSample(void)
    {
    bool success = false;

    CkStringBuilder sb;
    bool crlf = true;
    sb.AppendLine("Name: John Smith",crlf);
    sb.AppendLine("Name: Jack Johnson",crlf);
    sb.AppendLine("Name: Mary Adams",crlf);

    std::cout << sb.getAsString() << "\r\n";

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

    const char *pattern = "Name:\\s+(?<first>\\w+)\\s+(?<last>\\w+)";
    CkJsonObject json;
    json.put_EmitCompact(false);

    int timeoutMs = 2000;
    int numMatches = sb.RegexMatch(pattern,json,timeoutMs);
    if (numMatches < 0) {
        // Probably an error in the regular expression.
        // Suggestion: Use AI to help create and/or diagnose regular expressions.
        std::cout << sb.lastErrorText() << "\r\n";
        return;
    }

    // Examine the matches:
    std::cout << json.emit() << "\r\n";

    // 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");
    int idx_last = json.IntOf("named.last");

    int i = 0;
    int matchCount = json.SizeOfArray("match");
    while (i < matchCount) {
        std::cout << "Match " << (i + 1) << ":" << "\r\n";
        json.put_I(i);

        json.put_J(idx_first);
        std::cout << "first: " << json.stringOf("match[i].group[j].cap") << "\r\n";

        json.put_J(idx_last);
        std::cout << "first: " << json.stringOf("match[i].group[j].cap") << "\r\n";

        std::cout << "" << "\r\n";
        i = i + 1;
    }

    // Output is: 

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