componentsseparatedbystring by multiple separators in Swift - ios

Question

So here is the string s:
"Hi! How are you? I'm fine. It is 6 p.m. Thank you! That's it."
I want them to be separated to a array as:
["Hi", "How are you", "I'm fine", "It is 6 p.m", "Thank you", "That's it"]
Which means the separators should be ". " + "? " + "! "
I've tried:
let charSet = NSCharacterSet(charactersInString: ".?!")
let array = s.componentsSeparatedByCharactersInSet(charSet)
But it will separate p.m. to two elements too. Result:
["Hi", " How are you", " I'm fine", " It is 6 p", "m", " Thank you", " That's it"]
I've also tried
let array = s.componentsSeparatedByString(". ")
It works well for separating ". " but if I also want to separate "? ", "! ", it become messy.
So any way I can do it? Thanks!

Answer 1

There is a method provided that lets you enumerate a string. You can do so by words or sentences or other options. No need for regular expressions.
let s = "Hi! How are you? I'm fine. It is 6 p.m. Thank you! That's it."
var sentences = [String]()
s.enumerateSubstringsInRange(s.startIndex..<s.endIndex, options: .BySentences) {
substring, substringRange, enclosingRange, stop in
sentences.append(substring!)
}
print(sentences)
The result is:
["Hi! ", "How are you? ", "I\'m fine. ", "It is 6 p.m. ", "Thank you! ", "That\'s it."]

Answer 2

rmaddy's answer is correct (+1). A Swift 3 implementation is:
var sentences = [String]()
string.enumerateSubstrings(in: string.startIndex ..< string.endIndex, options: .bySentences) { substring, substringRange, enclosingRange, stop in
sentences.append(substring!)
}
You can also use regular expression, NSRegularExpression, though it's much hairier than rmaddy's .bySentences solution. In Swift 3:
var sentences = [String]()
let regex = try! NSRegularExpression(pattern: "(^|\\s+)(\\w.*?[.!?]+)(?=(\\s+|$))")
regex.enumerateMatches(in: string, range: NSMakeRange(0, string.characters.count)) { match, flags, stop in
sentences.append((string as NSString).substring(with: match!.rangeAt(2)))
}
Or Swift 2:
let regex = try! NSRegularExpression(pattern: "(^|\\s+)(\\w.*?[.!?]+)(?=(\\s+|$))", options: [])
var sentences = [String]()
regex.enumerateMatchesInString(string, options: [], range: NSMakeRange(0, string.characters.count)) { match, flags, stop in
sentences.append((string as NSString).substringWithRange(match!.rangeAtIndex(2)))
}
The [.!?] syntax matches any of those three characters. The | means "or". The ^ matches the start of the string. The $ matches the end of the string. The \\s matches a whitespace character. The \\w matches a "word" character. The * matches zero or more of the preceding character. The + matches one or more of the preceding character. The (?=) is a look-ahead assertion (e.g. see if there's something there, but don't advance through that match).
I've tried to simplify this a bit, and it's still pretty complicated. Regular expressions offer rich text pattern matching, but, admittedly, it is a little dense when you first use it. But this rendition matches (a) repeated punctuation (e.g. "Thank you!!!"), (b) leading spaces, and (c) trailing spaces, too.

Answer 3

If the splitting basis is something a little more esoteric than sentences, this extension could work.
extension String {
public func components(separatedBy separators: [String]) -> [String] {
var output: [String] = [self]
for separator in separators {
output = output.flatMap { $0.components(separatedBy: separator) }
}
return output.map { $0.trimmingCharacters(in: .whitespaces)}
}
}
let artists = "Rihanna, featuring Calvin Harris".components(separated by: [", with", ", featuring"])

Answer 4

I tried to find a regex to solve this too: (([^.!?]+\s)*\S+(\.|!|\?))
Here the explanation from regexper and an example

Answer 5

Well I've found a regex too from here
var pattern = "(?<=[.?!;…])\\s+(?=[\\p{Lu}\\p{N}])"
let s = "Hi! How are you? I'm fine. It is 6 p.m. Thank you! That's it."
let sReplaced = s.stringByReplacingOccurrencesOfString(pattern, withString:"[*-SENTENCE-*]" as String, options:NSStringCompareOptions.RegularExpressionSearch, range:nil)
let array = sReplaced.componentsSeparatedByString("[*-SENTENCE-*]")
Perhaps it's not a good way as it has to first replace and than separate the string. :)
UPDATE:
For regex part, if you also want to match Chinese/Japanese punctuations (which space after each punctuation is not necessary), you can use the following one:
((?<=[.?!;…])\\s+|(?<=[。！？；…])\\s*)(?=[\\p{L}\\p{N}])