Xojo Plugin

Regular Expression with Multiple Matches and Named Capture Groups

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Demonstrates regular expressions with named capture groups and multiple matches. Xojo Plugin

Dim success As Boolean
success = False

Dim sb As New Chilkat.StringBuilder
Dim crlf As Boolean
crlf = True
success = sb.AppendLine("Name: John Smith",crlf)
success = sb.AppendLine("Name: Jack Johnson",crlf)
success = sb.AppendLine("Name: Mary Adams",crlf)

System.DebugLog(sb.GetAsString())

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

Dim pattern As String
pattern = "Name:\s+(?<first>\w+)\s+(?<last>\w+)"
Dim json As New Chilkat.JsonObject
json.EmitCompact = False

Dim timeoutMs As Int32
timeoutMs = 2000
Dim numMatches As Int32
numMatches = sb.RegexMatch(pattern,json,timeoutMs)
If (numMatches < 0) Then
    // Probably an error in the regular expression.
    // Suggestion: Use AI to help create and/or diagnose regular expressions.
    System.DebugLog(sb.LastErrorText)
    Return
End If

// Examine the matches:
System.DebugLog(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:

Dim idx_first As Int32
idx_first = json.IntOf("named.first")
Dim idx_last As Int32
idx_last = json.IntOf("named.last")

Dim i As Int32
i = 0
Dim matchCount As Int32
matchCount = json.SizeOfArray("match")
While i < matchCount
    System.DebugLog("Match " + Str(i + 1) + ":")
    json.I = i

    json.J = idx_first
    System.DebugLog("first: " + json.StringOf("match[i].group[j].cap"))

    json.J = idx_last
    System.DebugLog("first: " + json.StringOf("match[i].group[j].cap"))

    System.DebugLog("")
    i = i + 1
Wend

// Output is: 

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