Rust Requires Chilkat v11.1.0+

Regular Expression Replace Capture Groups

See more Regular Expressions Examples

Demonstrates replacing capture groups for a regular expression.

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

Rust

let subject = "John Anders, +_+_+ Mary Robins $$$$".to_string();
let pattern = "(?<first>\\w+)\\s+(?<last>\\w+)".to_string();

let sb = chilkat::StringBuilder::new();
let _ = sb.append(&subject);

let json = chilkat::JsonObject::new();
json.set_emit_compact(false);

let timeout_ms = 2000;
let mut num_matches = sb.regex_match(&pattern, &json, timeout_ms);
if num_matches < 0 {
    // Probably an error in the regular expression.
    // Suggestion: Use AI to help create and/or diagnose regular expressions.
    println!("{}", sb.last_error_text());
    return;
}

// Examine the matches:
println!("{}", json.emit().unwrap_or_default());

// There are 2 matches:

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "John Anders",
//           "idx": 0,
//           "len": 11
//         },
//         {
//           "cap": "John",
//           "idx": 0,
//           "len": 4
//         },
//         {
//           "cap": "Anders",
//           "idx": 5,
//           "len": 6
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Mary Robins",
//           "idx": 19,
//           "len": 11
//         },
//         {
//           "cap": "Mary",
//           "idx": 19,
//           "len": 4
//         },
//         {
//           "cap": "Robins",
//           "idx": 24,
//           "len": 6
//         }
//       ]
//     }
//   ]
// }

// To replace capture groups, write code to examine each capture group within
// each match, and provide a replacement string.
// Then call RegexReplace.

// For example, let's capitalize the first names, and add append "on" to the last name.
// After doing replacements, we should get:  JOHN Anderson, +_+_+ MARY Robinson $$$$

let first_name_idx = json.int_of("named.first");
let last_name_idx = json.int_of("named.last");

let sb_temp = chilkat::StringBuilder::new();

let mut i = 0;
num_matches = json.size_of_array("match");
while i < num_matches {

    json.set_i(i);

    // The replacement string for the first name will be all uppercase.
    json.set_j(first_name_idx);
    sb_temp.clear();
    let _ = json.string_of_sb("match[i].group[j].cap", &sb_temp);
    let _ = sb_temp.to_uppercase();
    let _ = json.update_sb("match[i].group[j].rep", &sb_temp);

    // Append "on" to the last name.
    json.set_j(last_name_idx);
    sb_temp.clear();
    let _ = json.string_of_sb("match[i].group[j].cap", &sb_temp);
    let _ = sb_temp.append("on");
    let _ = json.update_sb("match[i].group[j].rep", &sb_temp);

    i = i + 1;
}

// The JSON now has replacement strings:
println!("{}", json.emit().unwrap_or_default());

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "John Anders",
//           "idx": 0,
//           "len": 11
//         },
//         {
//           "cap": "John",
//           "idx": 0,
//           "len": 4,
//           "rep": "JOHN"
//         },
//         {
//           "cap": "Anders",
//           "idx": 5,
//           "len": 6,
//           "rep": "Anderson"
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Mary Robins",
//           "idx": 19,
//           "len": 11
//         },
//         {
//           "cap": "Mary",
//           "idx": 19,
//           "len": 4,
//           "rep": "MARY"
//         },
//         {
//           "cap": "Robins",
//           "idx": 24,
//           "len": 6,
//           "rep": "Robinson"
//         }
//       ]
//     }
//   ]
// }

// Call RegexReplace to update the StringBuilder with the replacements.
if sb.regex_replace(&json).is_err() {
    println!("{}", sb.last_error_text());
    return;
}

println!("Result after doing replacements:");
println!("{}", sb.get_as_string().unwrap_or_default());

// Result after doing replacements:
// JOHN Anderson, +_+_+ MARY Robinson $$$$