Swift: Background gradient for UIView

Update your method to the code blow:

func setGradientBackground(colorTop: UIColor, colorBottom: UIColor){
    let gradientLayer = CAGradientLayer()
    gradientLayer.colors = [colorTop.cgColor, colorBottom.cgColor]
    gradientLayer.startPoint = CGPoint(x: 0.5, y: 1.0)
    gradientLayer.endPoint = CGPoint(x: 0.5, y: 0.0)
    gradientLayer.locations = [NSNumber(floatLiteral: 0.0), NSNumber(floatLiteral: 1.0)]
    gradientLayer.frame = self.bounds

    self.layer.insertSublayer(gradientLayer, at: 0)
}

Moayad's answer worked best for me but it was backwards with top color as bottom so i reversed the function he posted.

Swift 4

    func setGradientBackground(colorTop: UIColor, colorBottom: UIColor){
        let gradientLayer = CAGradientLayer()
        gradientLayer.colors = [colorBottom.cgColor, colorTop.cgColor]
        gradientLayer.startPoint = CGPoint(x: 0.5, y: 1.0)
        gradientLayer.endPoint = CGPoint(x: 0.5, y: 0.0)
        gradientLayer.locations = [0, 1]
        gradientLayer.frame = bounds

        layer.insertSublayer(gradientLayer, at: 0)
}

For @IBDesignable: You can custom your UI on storyboard. It is easier to use.

@IBDesignable class GradientView: UIView {

    @IBInspectable var startColor: UIColor = .blue {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var endColor: UIColor = .green {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var shadowColor: UIColor = .yellow {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var shadowX: CGFloat = 0 {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var shadowY: CGFloat = -3 {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var shadowBlur: CGFloat = 3 {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var startPointX: CGFloat = 0 {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var startPointY: CGFloat = 0 {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var endPointX: CGFloat = 0 {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var endPointY: CGFloat = 0 {
        didSet {
            setNeedsLayout()
        }
    }

    @IBInspectable var cornerRadius: CGFloat = 0 {
        didSet {
            setNeedsLayout()
        }
    }

    override class var layerClass: AnyClass {
        return CAGradientLayer.self
    }

    override func layoutSubviews() {
        let gradientLayer = layer as! CAGradientLayer
        gradientLayer.colors = [startColor.cgColor, endColor.cgColor]
        gradientLayer.startPoint = CGPoint(x: startPointX, y: startPointY)
        gradientLayer.endPoint = CGPoint(x: endPointX, y: endPointY)
        layer.cornerRadius = cornerRadius
        layer.shadowColor = shadowColor.cgColor
        layer.shadowOffset = CGSize(width: shadowX, height: shadowY)
        layer.shadowRadius = shadowBlur
        layer.shadowOpacity = 1
    }
}

The code works fine. However, you should call it at layoutSubviews.

Swift 5

class ViewExample: UIView {

    // MARK: - Lifecycle
    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        configureGradientLayer()
    }

    func configureGradientLayer(){
        backgroundColor = .clear
        let gradient = CAGradientLayer()
        gradient.colors = [UIColor.systemPurple.cgColor, UIColor.systemPink.cgColor]
        gradient.locations = [0, 1]
        gradient.frame = bounds
        layer.addSublayer(gradient)
    }

}

This does work for my project

/**
 set a gradient to a view
 gradientColors must be cgColors
 gradientColors and locations must have the same array size
 example:
 let gradientColors = [UIColor.red.cgColor,UIColor.blue.cgColor,UIColor.yellow.cgColor]
 let locations:[NSNumber] = [0.0,0.8,1.0]
 */
static func setGradient(viewWithGradient: UIView, backgroundColor: UIColor, gradientColors: [CGColor], locations:[NSNumber], boundsOfGradient:CGRect) {

    if gradientColors.count != locations.count {
        print("gradientColors and locations must have same size!")
        return
    }

    viewWithGradient.backgroundColor = backgroundColor
    let mask = CAGradientLayer()
    mask.colors = gradientColors
    mask.locations = locations
    mask.frame = boundsOfGradient
    viewWithGradient.layer.mask = mask
}

Call like this

    let gradientColors = [UIColor.red.cgColor,UIColor.blue.cgColor,UIColor.yellow.cgColor]
    let locations:[NSNumber] = [0.0,0.8,1.0]
    GeneralTools.setGradient(viewWithGradient: yourViewThatShouldGetGradient, backgroundColor: backgroundColorOfYourViewWithGradient, gradientColors: gradientColors, locations: locations, boundsOfGradient: viewWhereIsYourGradientInside.bounds)

Maybe not clear enough boundsOfGradient: The bounds will be set to your gradients frame. So simply said this will declare the size of your gradient.

gmoraleda's answer is correct. Do this on viewDidLayoutSubviews if you're using AutoLayout.