import Foundation
let pattern = ##"""
# Define the opening and closing elements before the recursion occurs
(?(DEFINE)
(?<open_curly>\{)
(?<close_curly>\})
(?<open_square>\[)
(?<close_square>\])
(?P<open_pascal>(?i:\bbegin\b))
(?P<close_pascal>(?i:\bend\b))
(?P<open_lua>--\[)
(?P<close_lua>--\])
(?<open>\g'open_curly'|\g'open_square'|\g'open_pascal'|\g'open_lua')
(?<close>\g'close_curly'|\g'close_square'|\g'close_pascal'|\g'close_lua')
)
# Match the opening element
(\g'open'
(?>
# For recursion, don't match either the opening
# or closing element
(?!\g'open'|\g'close')(.)
|
# Recurse this captured pattern
(?-1)
)*
# Match the closing element
\g'close')
"""##
let regex = try! NSRegularExpression(pattern: pattern, options: .allowCommentsAndWhitespace)
let testString = #"""
EVENLY BALANCED curly braces
{{{}}}
{ test1 { test2 { test3 { test4 } } } }
UNEVENLY BALANCED curly braces
{{{{}}}
{ test1 { test2 { test3 { test4 } } } } }
MULTI-LINE EVENLY BALANCED curly braces
{
}
MULTI-LINE UNEVENLY BALANCED curly braces
{{
}
EVENLY BALANCED square braces
[ test1 [ test2 [ test3 [ test4 ] ] ] ]
EVENLY BALANCED square and curly braces
{ test1 [ test2 { test3 [ test4 ] } ] }
UNEVENLY BALANCED square and curly braces
{ test1 [ test2 { test3 [ test4 ] } } ]
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let matches = regex.matches(in: testString, range: stringRange)
var result: [[String]] = []
for match in matches {
var groups: [String] = []
for rangeIndex in 1 ..< match.numberOfRanges {
let nsRange = match.range(at: rangeIndex)
guard !NSEqualRanges(nsRange, NSMakeRange(NSNotFound, 0)) else { continue }
let string = (testString as NSString).substring(with: nsRange)
groups.append(string)
}
if !groups.isEmpty {
result.append(groups)
}
}
print(result)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression