VB.NET

Regular Expression with Multiple Matches and Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups and multiple matches. VB.NET

Dim success As Boolean = False

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

Debug.WriteLine(sb.GetAsString())

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

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

Dim timeoutMs As Integer = 2000
Dim numMatches As Integer = 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.
    Debug.WriteLine(sb.LastErrorText)
    Exit Sub
End If


' Examine the matches:
Debug.WriteLine(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 Integer = json.IntOf("named.first")
Dim idx_last As Integer = json.IntOf("named.last")

Dim i As Integer = 0
Dim matchCount As Integer = json.SizeOfArray("match")
While i < matchCount
    Debug.WriteLine("Match " & (i + 1) & ":")
    json.I = i

    json.J = idx_first
    Debug.WriteLine("first: " & json.StringOf("match[i].group[j].cap"))

    json.J = idx_last
    Debug.WriteLine("first: " & json.StringOf("match[i].group[j].cap"))

    Debug.WriteLine("")
    i = i + 1
End While

' Output is: 

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