SwiftGradientLabel

import CoreGraphics

import Foundation
import UIKit

class GradientLabel : UILabel {

    let gradient:               CGGradient!
    let alignedToSuperview:     Bool!

    init(colors: [UIColor]!, locations: [CGFloat]!, alignedToSuperview: Bool = true) {
        super.init(frame: CGRect.zeroRect)

        let gradientColors = colors.map {(color: UIColor!) -> AnyObject! in return color.CGColor as AnyObject! } as NSArray
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        self.gradient = CGGradientCreateWithColors(colorSpace, gradientColors, locations)
        self.alignedToSuperview = alignedToSuperview
    }

    override func drawTextInRect(rect: CGRect) {
        let context = UIGraphicsGetCurrentContext()

        // create the mask by drawing in the context first
        CGContextSaveGState(context) ;
        CGContextSetTextDrawingMode(context, kCGTextFill) ;

        super.drawTextInRect(rect) ;

        let lines = CGRect (origin: CGPoint(x: 0, y:16.0), size: CGSize(width: 160.0, height: 2.0)) ;
        CGContextSetFillColorWithColor(context, UIColor.whiteColor().CGColor) ;
        CGContextFillRect(context, lines) ;

        // snapshot the context into the just created mask
        let alphaMask = CGBitmapContextCreateImage(context) ;

        CGContextClearRect(context, rect) ;

        CGContextTranslateCTM(context, 0, rect.size.height);
        CGContextScaleCTM(context, 1.0, -1.0);

        // Clip the current context to our alphaMask
        CGContextClipToMask(context, rect, alphaMask);

        let startPoint = CGPoint(x:0.0, y: 0.0)
        let endPoint = CGPoint(x:self.superview.bounds.size.width, y: 0.0)

        if self.alignedToSuperview {
            CGContextTranslateCTM(context, -1.0 * self.frame.origin.x, 0.0)
        }
        
// As of Xcode 6 beta 4, CGGradientDrawingOptions does not play well with Int and UInt32 confusion ...

//        var options: CGGradientDrawingOptions = kCGGradientDrawsBeforeStartLocation as CGGradientDrawingOptions
//            | kCGGradientDrawsAfterEndLocation GGradientDrawsBeforeStartLocation as UInt32 ;
//        CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, options) ;
        CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 3)

        CGContextRestoreGState(context)
    }
}

sample use:

        self.grLabel2 = GradientLabel(colors:[UIColor.whiteColor(), UIColor.greenColor(), UIColor.orangeColor()], locations:[0.0, 0.75, 1.0])
        self.grLabel2.textColor = TEXT_GRADIENT_COLOR ;
        self.grLabel2.font = TOOLBAR_TITLE_FONT

        self.grLabel2.text = "Swift Gradient"
        self.grLabel2.sizeToFit()

        self.grLabel2.frame = self.grLabel2.frame.rectByCenteringXIntoRect(UIScreen.mainScreen().bounds)
        self.grLabel2.frame.origin.y += 20.0
        self.addSubview(self.grLabel2)

using:

extension CGRect {

    var center : CGPoint {
        return CGPoint(
            x: self.origin.x + (self.size.width / 2.0)
        ,   y: self.origin.y + (self.size.height / 2.0)
        )
    }

    func rectByCenteringIntoRect(intoRect: CGRect) -> CGRect {
        var rect = self
        rect.origin.x = (intoRect.size.width  - rect.size.width) / 2.0
        rect.origin.y = (intoRect.size.height - rect.size.height) / 2.0
        return rect
    }
}