daltoniam/bumblebee

import Bumblebee

//add the label to the view
let label = UILabel(frame: CGRect(x: 0, y: 65, width: view.frame.size.width, height: 400))
label.numberOfLines = 0
view.addSubview(label)

let rawText = "Hello I am *red* and I am __bold__. [link here](http://vluxe.io/) Here is an image: ![](http://imgs.xkcd.com/comics/encoding.png). This is a second link: [Apple](https://apple.com). I like *turtles*"
parser.add(pattern: MDLinkPattern()) { (str, attributes) in
    let link = attributes![MDLinkPattern.linkAttribute]!
    return MatchedResponse(string: str, attributes: [NSAttributedStringKey.foregroundColor: UIColor.blue,
                                                     NSAttributedStringKey.link: URL(string: link)!])
}

parser.add(pattern: MDImagePattern()) { (str, attributes) in
    let link = attributes![MDImagePattern.linkAttribute]!
    let textAttachment = NSTextAttachment(data: nil, ofType: nil)
    HTTP.GET(link) { (response) in
        let img = UIImage(data: response.data)!
        textAttachment.image = UIImage(data: response.data)
        textAttachment.bounds = CGRect(x: 0, y: 0, width: img.size.width, height: img.size.height)
        DispatchQueue.main.async {
            label.setNeedsDisplay() //tell our label to redraw now that we have our image
        }
    }
    return MatchedResponse(string: str, attributes: [NSAttributedStringKey.attachment: textAttachment])
}

parser.add(pattern: MDBoldPattern()) { (str, attributes) in
    return MatchedResponse(string: str, attributes: [NSAttributedStringKey.font: UIFont.boldSystemFont(ofSize: 17)])
}

parser.add(pattern: MDEmphasisPattern()) { (str, attributes) in
    return MatchedResponse(string: str, attributes: [NSAttributedStringKey.foregroundColor: UIColor.red])
}

parser.process(text: rawText) { (attrString) in
    label.attributedText = attrString
}

//Matches URLs. e.g. (http://domain.com/url/etc)
public struct LinkPattern : Pattern {
    public init() {} //only need to allow public initialization
    public func regex() throws -> NSRegularExpression {
        return try NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)
    }
}

//Matches typical user name patterns from social platforms like twitter. (@daltoniam, etc)
public struct UserNamePattern : Pattern {
    public init() {} //only need to allow public initialization
    public func regex() throws -> NSRegularExpression {
        //twitter requires between 4 and 15 char for a user name, but hightlights the user name at one char...
        //so I'm using {1,15} instead of {4,15}, but could be easily changed depending on requirements
        return try NSRegularExpression(pattern: "(?<=\\s|^)@[a-zA-Z0-9_]{1,15}\\b", options: .caseInsensitive)
    }
}

//Matches hex strings to convert them to their proper unicode version.
public struct UnicodePattern : Pattern {
    public init() {} //only need to allow public initialization
    public func regex() throws -> NSRegularExpression {
        return try NSRegularExpression(pattern: "(?<=\\s|^)U\\+[a-zA-Z0-9]{2,6}\\b", options: .caseInsensitive)
    }
    
    //The transform method allows a pattern to do pre processing on the text before it shows up in the matched closure.
    //convert the hex to its proper Unicode scalar. e.g. (U+1F602 to 😂)
    public func transform(text: String) -> (text: String, attributes: [String: String]?) {
        let offset = text.index(text.startIndex, offsetBy: 2)
        let hex = String(text[offset..<text.endIndex])
        if let i = Int(hex, radix: 16) {
            let scalar = UnicodeScalar(i)
            if let scalar = scalar {
                return (text: String(Character(scalar)), attributes: nil)
            }
        }
        return (text: text, attributes: nil)
    }
}

//your custom pattern!
public struct MyCustomPattern : Pattern {
    public init() {} //only need to allow public initialization
    public func regex() throws -> NSRegularExpression {
        return try NSDataDetector(types: NSTextCheckingResult.CheckingType.address.rawValue)
    }
}

//your custom pattern here!
parser.add(pattern: MyCustomPattern()) { (str, attributes) in
    return MatchedResponse(string: str, attributes: [NSAttributedStringKey.foregroundColor: UIColor.purple])
}