Gradient Mask v. Gradient Layer

gradient-playground

import UIKit
import XCPlayground

import UIKit

final public class GradientView: UIView {
    
    override public class func layerClass() -> AnyClass {
        return CAGradientLayer.self
    }
    
    public var colors: [AnyObject]? {
        set {
            gradientLayer.colors = newValue
        }
        
        get {
            return gradientLayer.colors
        }
    }
    
    // MARK: - Private
    
    private lazy var gradientLayer: CAGradientLayer = {
        return self.layer as! CAGradientLayer
    }()
}


let backgroundColor = UIColor.magentaColor()
let gradientColor = UIColor.purpleColor()

let containerView = UIView(frame: CGRect(x: 0.0, y: 0.0, width: 400, height: 400))
containerView.backgroundColor = backgroundColor
XCPlaygroundPage.currentPage.liveView = containerView

let gradientView = GradientView(frame: CGRect(x: 0, y: 200, width: 200, height: 200))
gradientView.backgroundColor = .clearColor()
gradientView.colors = [
    UIColor.clearColor().CGColor,
    gradientColor.CGColor
]
containerView.addSubview(gradientView)

let gradientView1 = GradientView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
gradientView1.backgroundColor = .clearColor()
gradientView1.colors = [
    UIColor.clearColor().CGColor,
    gradientColor.CGColor
]
containerView.addSubview(gradientView1)

let view = UIView(frame: CGRect(x: 200, y: 200, width: 200, height: 200))
view.backgroundColor = .clearColor()

let gradientMask = CAGradientLayer()
gradientMask.frame = view.bounds
gradientMask.colors = [
    UIColor.clearColor().CGColor,
    UIColor.blackColor().CGColor
]
view.backgroundColor = gradientColor

view.layer.mask = gradientMask

containerView.addSubview(view)

let view1 = UIView(frame: CGRect(x: 200, y: 0, width: 200, height: 200))
view1.backgroundColor = .clearColor()

let gradientMask1 = CAGradientLayer()
gradientMask1.frame = view1.bounds
gradientMask1.colors = [
    UIColor.clearColor().CGColor,
    UIColor.blackColor().CGColor
]
view1.backgroundColor = gradientColor

view1.layer.mask = gradientMask1

containerView.addSubview(view1)


let label = UILabel(frame: gradientView.bounds)
label.textAlignment = .Center
label.textColor = .whiteColor()
label.font = UIFont.boldSystemFontOfSize(200)
label.text = "A"
gradientView.addSubview(label)

let label1 = UILabel(frame: view.bounds)
label1.textAlignment = .Center
label1.textColor = .whiteColor()
label1.font = UIFont.boldSystemFontOfSize(200)
label1.text = "A"
view.addSubview(label1)