UIViewGradientExtension.swift

import UIKit

typealias GradientPoints = (startPoint: CGPoint, endPoint: CGPoint)

enum GradientOrientation {
    case horizontal
    case vertical
    
    var startPoint: CGPoint {
        return points.startPoint
    }
    
    var endPoint: CGPoint {
        return points.endPoint
    }
    
    var points: GradientPoints {
        switch self {
            case .horizontal:
                return (CGPoint.init(x: 0.0, y: 0.5), CGPoint.init(x: 1.0, y: 0.5))
            case .vertical:
                return (CGPoint.init(x: 0.0, y: 0.0), CGPoint.init(x: 0.0, y: 1.0))
        }
    }
}

extension UIView {
    
    func applyGradient(withColours colours: [UIColor], gradientOrientation orientation: GradientOrientation, locations: [NSNumber]? = nil) {
        let gradient: CAGradientLayer = CAGradientLayer()
        gradient.frame = bounds
        gradient.colors = colours.map { $0.cgColor }
        gradient.startPoint = orientation.startPoint
        gradient.endPoint = orientation.endPoint
        gradient.locations = locations
        layer.insertSublayer(gradient, at: 0)
    }
}