Show link text on NSTextField for OS X by swift.

link_string.swift

class AppDelegate, NSObject, NSApplicationDelegate {

    @IBOutlet weak var linkField: NSTextField!

    func applicationDidFinishLaunching(aNotification: NSNotification) {
        ...
        linkField.attributedStringValue = link_string("Google", url: NSURL(string: "http://www.google.com/"))
        ...
    }

    func link_string(text:String, url:NSURL) -> NSMutableAttributedString {
        // initially set viewable text
        var attrString = NSMutableAttributedString(string: text)
        var range = NSRange(location: 0, length: attrString.length)
        attrString.beginEditing()
        // stack URL
        attrString.addAttribute(NSLinkAttributeName,
            value: url.absoluteString!, range: range)
        // stack text color
        attrString.addAttribute(NSForegroundColorAttributeName,
            value: NSColor.blueColor(), range: range)
        // stack underline attribute
        attrString.addAttribute(NSUnderlineStyleAttributeName,
            value: NSSingleUnderlineStyle, range: range)
        attrString.endEditing()
        return attrString
    }
}