Horizontal gradient

func drawHorizontalGradient(over container : UIView, left leftColor: UIColor, right rightColor: UIColor) {
    let maskLayer = CAGradientLayer()
    maskLayer.colors = [leftColor.CGColor, rightColor.CGColor]
    maskLayer.startPoint = CGPointMake(0.0, 0.5)
    maskLayer.endPoint = CGPointMake(1.0, 0.5)
    maskLayer.bounds = container.bounds
    maskLayer.anchorPoint = CGPointZero
    container.layer.insertSublayer(maskLayer, atIndex: 0)
}