B4X Requires Chilkat v11.1.0+

Regular Expression with Multiple Matches and Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups and multiple matches. B4X

Dim success As Boolean = False

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

Log(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 ChilkatJsonObject
json.Initialize
json.EmitCompact = False

Dim timeoutMs As Int = 2000
Dim numMatches As Int = 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.
    Log(sb.LastErrorText)
    Return
End If


'  Examine the matches:
Log(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 Int = json.IntOf("named.first")
Dim idx_last As Int = json.IntOf("named.last")

Dim i As Int = 0
Dim matchCount As Int = json.SizeOfArray("match")
Do While i < matchCount
    Log("Match " & (i + 1) & ":")
    json.I = i

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

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

    Log("")
    i = i + 1
Loop

'  Output is: 

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