这是一个快速扩展，你可以通过任意数量的颜色。在插入一个渐变图层之前，它会删除之前的任何渐变图层，如果需要的话，它会返回新插入的渐变图层进行进一步的操作:

    extension UIView {

    /**
     Given an Array of CGColor, it will:
        - Remove all sublayers of type CAGradientLayer.
        - Create and insert a new CAGradientLayer.

     - Parameters: 
        - colors: An Array of CGColor with the colors for the gradient fill

     - Returns: The newly created gradient CAGradientLayer
     */
    func layerGradient(colors c:[CGColor])->CAGradientLayer {
        self.layer.sublayers = self.layer.sublayers?.filter(){!($0 is CAGradientLayer)}
        let layer : CAGradientLayer = CAGradientLayer()
        layer.frame.size = self.frame.size
        layer.frame.origin = CGPointZero
        layer.colors = c
        self.layer.insertSublayer(layer, atIndex: 0)
        return layer
    }
}

添加渐变到图层，添加:

let layer = CAGradientLayer()
layer.frame = CGRect(x: 64, y: 64, width: 120, height: 120)
layer.colors = [UIColor.red.cgColor, UIColor.blue.cgColor]
view.layer.addSublayer(layer)

这段代码将与Swift 3.0一起工作

class GradientView: UIView {

    override open class var layerClass: AnyClass {
        get{
            return CAGradientLayer.classForCoder()
        }
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        let gradientLayer = self.layer as! CAGradientLayer
        let color1 = UIColor.white.withAlphaComponent(0.1).cgColor as CGColor
        let color2 = UIColor.white.withAlphaComponent(0.9).cgColor as CGColor
        gradientLayer.locations = [0.60, 1.0]
        gradientLayer.colors = [color2, color1]
    }
}

对于swift应用CAGradientLayer到任何对象(水平和垂直)

func makeGradientColor(`for` object : AnyObject , startPoint : CGPoint , endPoint : CGPoint) -> CAGradientLayer {
    let gradient: CAGradientLayer = CAGradientLayer()

    gradient.colors = [(UIColor(red: 59.0/255.0, green: 187.0/255.0, blue: 182.0/255.0, alpha: 1.00).cgColor), (UIColor(red: 57.0/255.0, green: 174.0/255.0, blue: 236.0/255.0, alpha: 1.00).cgColor)]
    gradient.locations = [0.0 , 1.0]

    gradient.startPoint = startPoint
    gradient.endPoint = endPoint
    gradient.frame = CGRect(x: 0.0, y: 0.0, width: object.frame.size.width, height: object.frame.size.height)
    return gradient
}

如何使用

let start : CGPoint = CGPoint(x: 0.0, y: 1.0)
let end : CGPoint = CGPoint(x: 1.0, y: 1.0)
let gradient: CAGradientLayer = self.makeGradientColor(for: vwTop, startPoint: start, endPoint: end)
vwTop.layer.insertSublayer(gradient, at: 0)

let start1 : CGPoint = CGPoint(x: 1.0, y: 1.0)
let end1 : CGPoint = CGPoint(x: 1.0, y: 0.0)
let gradient1: CAGradientLayer = self.makeGradientColor(for: vwTop, startPoint: start1, endPoint: end1)
vwBottom.layer.insertSublayer(gradient1, at: 0)

您可以在这里检查输出

如果你想使用HEX而不是RGBA，只需拖动一个新的空的.swift并添加下面提到的代码:

     import UIKit

    extension UIColor {
        convenience init(rgba: String) {
            var red:   CGFloat = 0.0
            var green: CGFloat = 0.0
            var blue:  CGFloat = 0.0
            var alpha: CGFloat = 1.0

            if rgba.hasPrefix("#") {
                let index   = advance(rgba.startIndex, 1)
                let hex     = rgba.substringFromIndex(index)
                let scanner = NSScanner(string: hex)
                var hexValue: CUnsignedLongLong = 0
                if scanner.scanHexLongLong(&hexValue) {
                    switch (count(hex)) {
                    case 3:
                        red   = CGFloat((hexValue & 0xF00) >> 8)       / 15.0
                        green = CGFloat((hexValue & 0x0F0) >> 4)       / 15.0
                        blue  = CGFloat(hexValue & 0x00F)              / 15.0
                    case 4:
                        red   = CGFloat((hexValue & 0xF000) >> 12)     / 15.0
                        green = CGFloat((hexValue & 0x0F00) >> 8)      / 15.0
                        blue  = CGFloat((hexValue & 0x00F0) >> 4)      / 15.0
                        alpha = CGFloat(hexValue & 0x000F)             / 15.0
                    case 6:
                        red   = CGFloat((hexValue & 0xFF0000) >> 16)   / 255.0
                        green = CGFloat((hexValue & 0x00FF00) >> 8)    / 255.0
                        blue  = CGFloat(hexValue & 0x0000FF)           / 255.0
                    case 8:
                        red   = CGFloat((hexValue & 0xFF000000) >> 24) / 255.0
                        green = CGFloat((hexValue & 0x00FF0000) >> 16) / 255.0
                        blue  = CGFloat((hexValue & 0x0000FF00) >> 8)  / 255.0
                        alpha = CGFloat(hexValue & 0x000000FF)         / 255.0
                    default:
                        print("Invalid RGB string, number of characters after '#' should be either 3, 4, 6 or 8")
                    }
                } else {
                    println("Scan hex error")
                }
            } else {
                print("Invalid RGB string, missing '#' as prefix")
            }
            self.init(red:red, green:green, blue:blue, alpha:alpha)
        }
}

类似地，拖动另一个空的.swift文件并添加下面提到的代码:

    class Colors {
    let colorTop = UIColor(rgba: "##8968CD").CGColor
    let colorBottom = UIColor(rgba: "#5D478B").CGColor

    let gl: CAGradientLayer

    init() {
        gl = CAGradientLayer()
        gl.colors = [ colorTop, colorBottom]
        gl.locations = [ 0.0, 1.0]
    }
}

然后在视图控制器中，在类下面实例化你的Color类，像这样:

let colors = Colors()

添加一个新函数:

func refresh() {
        view.backgroundColor = UIColor.clearColor()
        var backgroundLayer = colors.gl
        backgroundLayer.frame = view.frame
        view.layer.insertSublayer(backgroundLayer, atIndex: 0)
    }

在viewDidLoad中声明函数:

refresh()

你完成了:)) 如果与RGBA相比，使用HEX太容易了。: D

易于使用的扩展swift 3

extension CALayer {
    func addGradienBorder(colors:[UIColor] = [UIColor.red,UIColor.blue], width:CGFloat = 1) {
        let gradientLayer = CAGradientLayer()
        gradientLayer.frame =  CGRect(origin: .zero, size: self.bounds.size)
        gradientLayer.startPoint = CGPoint(x:0.0, y:0.5)
        gradientLayer.endPoint = CGPoint(x:1.0, y:0.5)
        gradientLayer.colors = colors.map({$0.cgColor})

        let shapeLayer = CAShapeLayer()
        shapeLayer.lineWidth = width
        shapeLayer.path = UIBezierPath(rect: self.bounds).cgPath
        shapeLayer.fillColor = nil
        shapeLayer.strokeColor = UIColor.black.cgColor
        gradientLayer.mask = shapeLayer

        self.addSublayer(gradientLayer)
    }
}

用你的观点，例子

yourView.addGradienBorder(color: UIColor.black, opacity: 0.1, offset: CGSize(width:2 , height: 5), radius: 3, viewCornerRadius: 3.0)