ツイート文字数カウント #CodePiece

CodePiece.swift

import UIKit

extension String {
    var length: Int {
        return self.characters.count
    }

    fileprivate var short_url_length: Int {
        return 23
    }

    var tweetCount: Int {
        guard let url_regex = try? NSRegularExpression(pattern: "https?://[\\w/:%#\\$&\\?\\(\\)~\\.=\\+\\-]+", options: .caseInsensitive) else {
            return 0
        }
        let url_regex_result = url_regex.matches(in: self, range: NSRange(location: 0, length: self.length))
        let url_count = url_regex_result.count
        let original_url_text = url_regex_result.reduce(0) {
            $1.range.length+$0
        }

        return self.length - original_url_text + short_url_length * url_count
    }
}