How do I process splitting on certain characters with regex - regex

Question

In my app, I'm trying to split a string into an array based on a regex pattern. I'd like to be able to load my volt templates and run them through our custom rendering engine - just to learn a bit more on how rendering engines work.
I wrote the regex below to do just that:
"(?s)(\\{\\{.*?\\}\\}|\\{%.*?%\\}|\\{#.*?#\\})"
And this is an example of such a template:
# {{ title }}
{{created_at}} {{created_location}}
============
Paragraphs are separated by a blank line.
2nd paragraph. *Italic*, **bold**, and `monospace`.
Itemized lists look like:
{% for (item in items) %}
* {{ item }}
{% endfor %}
Now, ideally, I'd like this to be converted to an array looking like this:
[
"# ",
"{{ title }}",
"\n",
"{{created_at}}",
" ",
"{{created_location}}",
"\n============\nParagraphs are separated by a blank line\n2nd paragraph. *Italic*, **bold**, and `monospace`.\n\nItemized lists look like:"
"{% for (item in items) %}",
"\n* {{ item }}\n",
"{% endfor %}"
]
However, when I run the regex above, I get:
[
"Paragraphs are separated by a blank line.\n2nd paragraph. *Italic*, **bold**, and `monospace`.\n\nItemized lists look like:",
"{% for (item in items) %}\n* {{ item }}",
"{% endfor %}\n"
]
As you can see the title part completely disappears. Furthermore, there seem to be some issues with the newline characters. Any ideas how I could solve this?

Answer 1

The problem wasn't in the regex, but in the code that I was using to split on the regex. I modified the code below to also return the regex itself.
extension NSRegularExpression {
func split(_ str: String) -> [String] {
let range = NSRange(location: 0, length: str.characters.count)
//get locations of matches
var matchingRanges: [NSRange] = []
let matches: [NSTextCheckingResult] = self.matches(in: str, options: [], range: range)
for match: NSTextCheckingResult in matches {
matchingRanges.append(match.range)
}
//invert ranges - get ranges of non-matched pieces
var pieceRanges: [NSRange] = []
//add first range
pieceRanges.append(NSRange(location: 0, length: (matchingRanges.count == 0 ? str.characters.count : matchingRanges[0].location)))
var endLoc: Int = 0
var startLoc: Int = 0
//add between splits ranges and last range
for i in 0..<matchingRanges.count {
let isLast = i + 1 == matchingRanges.count
let location = matchingRanges[i].location
let length = matchingRanges[i].length
startLoc = location + length
endLoc = isLast ? str.characters.count : matchingRanges[i + 1].location
pieceRanges.append(NSRange(location: startLoc, length: endLoc - startLoc))
}
var pieces: [String] = []
var previous: NSRange = NSRange(location: 0, length: 0)
for range: NSRange in pieceRanges {
let item = (str as NSString).substring(with: NSRange(location:previous.location+previous.length, length:range.location-(previous.location+previous.length)))
pieces.append(item)
let piece = (str as NSString).substring(with: range)
pieces.append(piece)
previous = range
}
return pieces
}
}