添加渐变层(swift 2.3)

import UIKit

class GradientView: UIView {
    override class var layerClass: AnyClass {
        return CAGradientLayer.self
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        
        if let gradientLayer = layer as? CAGradientLayer {
            gradientLayer.colors = [UIColor.red.cgColor, UIColor.blue.cgColor]
            gradientLayer.startPoint = CGPoint(x: 0, y: 0)
            gradientLayer.endPoint = CGPoint(x: 1, y: 1)
        }
    }
}

// 在ViewController中使用GradientView
class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let gradientView = GradientView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
        view.addSubview(gradientView)
    }
}