Functional NSAttributedString to NSAttributedString with added colour, highlight and underline

gistfile1.swift

typealias Attributer = NSAttributedString -> NSAttributedString

func color(color:UIColor) -> Attributer {
    return {(aString:NSAttributedString) in
        let mString = aString.mutableCopy()
        mString.addAttribute(NSForegroundColorAttributeName, value: color, range:  NSRange(location: 0, length: aString.length))
        return mString.copy() as! NSAttributedString
    }
    
}

func underline(style:NSUnderlineStyle) -> Attributer {
    return {aString in
        let mString = aString.mutableCopy()
        mString.addAttribute(NSUnderlineStyleAttributeName, value: style.rawValue, range:  NSRange(location: 0, length: aString.length))
        return mString.copy() as! NSAttributedString
    }
    
}

func highlight(color:UIColor) -> Attributer {
    return {(aString:NSAttributedString) in
        let mString = aString.mutableCopy()
        mString.addAttribute(NSBackgroundColorAttributeName, value: color, range:  NSRange(location: 0, length: aString.length))
        return mString.copy() as! NSAttributedString
    }
}

let aString = NSAttributedString(string: "Hello Swift!")

let addUnderline = underline(NSUnderlineStyle.StyleSingle)
let addColor = color(UIColor.brownColor())
let addHighlight = highlight(UIColor.yellowColor())

addColor(aString)
addUnderline(aString)
addHighlight(aString)