Functional Programming: Custom Operator in Swift

gistfile1.swift

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

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

infix operator >>> { associativity left }

func >>> (attributer1:Attributer,attributer2:Attributer) -> Attributer {
    return {aString in attributer1(attributer2(aString))}
    
}


let combo = color(UIColor.blueColor())
    >>> highlight(UIColor.yellowColor())
    >>> underline(NSUnderlineStyle.StyleDouble)

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