Property to Convert String to Shipper URL if Tracking Number Matches Regex

Regex.swift

import UIKit

infix operator =~

func =~ (value : String, pattern : String) -> RegexMatchResult {
    var err : NSError?
    let nsstr = value as NSString
    let options = NSRegularExpression.Options(rawValue: 0)
    let re: NSRegularExpression?
    do {
        re = try NSRegularExpression(pattern: pattern, options: options)
    } catch let error as NSError {
        err = error
        re = nil
    }
    if let _ = err {
        return RegexMatchResult(items: [])
    }
    let all = NSRange(location: 0, length: nsstr.length)
    let moptions = NSRegularExpression.MatchingOptions(rawValue: 0)
    var matches = [String]()
    re!.enumerateMatches(in: value, options: moptions, range: all) {
        (result : NSTextCheckingResult?, flags : NSRegularExpression.MatchingFlags, ptr : UnsafeMutablePointer<ObjCBool>) in
        let string = nsstr.substring(with: result!.range)
        matches.append(string)
    }
    return RegexMatchResult(items: matches)
}

struct RegexMatchCaptureGenerator : IteratorProtocol {
    mutating func next() -> String? {
        if items.isEmpty { return nil }
        let ret = items[0]
        items = items[1..<items.count]
        return ret
    }
    var items: ArraySlice<String>
}

struct RegexMatchResult : Sequence {
    var items: [String]
    func makeIterator() -> RegexMatchCaptureGenerator {
        return RegexMatchCaptureGenerator(items: items[0..<items.count])
    }
    var boolValue: Bool {
        return items.count > 0
    }
    subscript (i: Int) -> String {
        return items[i]
    }
}

String+Extensions.swift

extension String {
    var shippingLink : URL? {
        let shippers =
            ["fedex" : ["regex" : "(\\b96\\d{20}\\b)|(\\b\\d{15}\\b)|(\\b\\d{12}\\b)",
                        "tracking_url" : "http://fedex.com/Tracking?action=track&language=english&cntry_code=us&tracknumbers=%@",
                        "name" : "FedEx"],
             "ups" : ["regex" : "\\b(1Z ?[0-9A-Z]{3} ?[0-9A-Z]{3} ?[0-9A-Z]{2} ?[0-9A-Z]{4} ?[0-9A-Z]{3} ?[0-9A-Z]|[\\dT]\\d\\d\\d ?\\d\\d\\d\\d ?\\d\\d\\d)\\b",
                      "tracking_url" : "http://wwwapps.ups.com/etracking/tracking.cgi?InquiryNumber1=%@&TypeOfInquiryNumber=T&AcceptUPSLicenseAgreement=yes&submit=Track",
                      "name" : "UPS"],
             "usps" : ["regex" : "\\b(9\\d\\d\\d ?\\d\\d\\d\\d ?\\d\\d\\d\\d ?\\d\\d\\d\\d ?\\d\\d\\d\\d ?\\d\\d|91\\d\\d ?\\d\\d\\d\\d ?\\d\\d\\d\\d ?\\d\\d\\d\\d ?\\d\\d\\d\\d)\\b",
                       "tracking_url" : "http://trkcnfrm1.smi.usps.com/PTSInternetWeb/InterLabelInquiry.do?origTrackNum=%@",
                       "name" : "US Postal Service"],
             "purolator" : ["regex" : "\\b((ANR|BXF|DCM|CGJ|YAW)[0-9]{9})\\b",
                       "tracking_url" : "https://www.purolator.com/purolator/ship-track/tracking-summary.page?pin=%@",
                       "name" : "Purolator"],
             "spee-dee" : ["regex" : "(SP\\d+)\\b",
                           "tracking_url" : "http://packages.speedeedelivery.com/index.php?barcodes=%@",
                           "name" : "Spee-Dee Delivery Service"]
        ]

        for (_, value) in shippers {
            // If the regex matches, build out the URL
            for _ in self =~ value["regex"]! {
              
                // Interpolate self (the tracking number) into the url String
                let urlString = String(format: (value["tracking_url"]!), self)
              
                // Return the resulting URL
                return URL(string: urlString)
            }
        }
        
        return nil
    }
}