Ruby

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

Ruby

require 'chilkat'

success = false

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

sb = Chilkat::CkStringBuilder.new()
sb.Append(subject)

json = Chilkat::CkJsonObject.new()
json.put_EmitCompact(false)

timeoutMs = 2000
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.
    print sb.lastErrorText() + "\n";
    exit
end

# Examine the matches:
print json.emit() + "\n";

# 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 $$$$

firstNameIdx = json.IntOf("named.first")
lastNameIdx = json.IntOf("named.last")

sbTemp = Chilkat::CkStringBuilder.new()

i = 0
numMatches = json.SizeOfArray("match")
while i < numMatches

    json.put_I(i)

    # The replacement string for the first name will be all uppercase.
    json.put_J(firstNameIdx)
    sbTemp.Clear()
    json.StringOfSb("match[i].group[j].cap",sbTemp)
    sbTemp.ToUppercase()
    json.UpdateSb("match[i].group[j].rep",sbTemp)

    # Append "on" to the last name.
    json.put_J(lastNameIdx)
    sbTemp.Clear()
    json.StringOfSb("match[i].group[j].cap",sbTemp)
    sbTemp.Append("on")
    json.UpdateSb("match[i].group[j].rep",sbTemp)

    i = i + 1
end

# The JSON now has replacement strings:
print json.emit() + "\n";

# {
#   "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.
success = sb.RegexReplace(json)
if (success == false)
    print sb.lastErrorText() + "\n";
    exit
end

print "Result after doing replacements:" + "\n";
print sb.getAsString() + "\n";

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