Gradient tint color in segmented control

I get gradient image with this method

func gradient(size:CGSize,color:[UIColor]) -> UIImage?{
    //turn color into cgcolor
    let colors = color.map{$0.cgColor}
    //begin graphics context
    UIGraphicsBeginImageContextWithOptions(size, true, 0.0)
    guard let context = UIGraphicsGetCurrentContext() else {
        return nil
    }
    // From now on, the context gets ended if any return happens
    defer {UIGraphicsEndImageContext()}
    //create core graphics context
    let locations:[CGFloat] = [0.0,1.0]
    guard let gredient = CGGradient.init(colorsSpace: CGColorSpaceCreateDeviceRGB(), colors: colors as NSArray as CFArray, locations: locations) else {
        return nil
    }
    //draw the gradient
    context.drawLinearGradient(gredient, start: CGPoint(x:0.0,y:size.height), end: CGPoint(x:size.width,y:size.height), options: [])
    // Generate the image (the defer takes care of closing the context)
    return UIGraphicsGetImageFromCurrentImageContext()
}

Then I set tintColor of segmented control to gradient:

    let gradientImage = gradient(size: listSegmentedControl.frame.size, color: [UIColor.black, UIColor.red])!
    listSegmentedControl.tintColor = UIColor(patternImage: gradientImage)

and that doesn't work. However, same code works for setting backgroundColor:

    let gradientImage = gradient(size: listSegmentedControl.frame.size, color: [UIColor.black, UIColor.red])!
    listSegmentedControl.backgroundColor = UIColor(patternImage: gradientImage)

Does anybody have any ideas why? I really need to set gradient tintColor. Any help is very appreciated.

EDIT:

Ideally I want my segmented control to look like this:

This is a known hack to change the tint color of UISegmentedControl

   let sortedViews = listSegmentedControl.subviews.sorted( by: { $0.frame.origin.x < $1.frame.origin.x } )

    for (index, view) in sortedViews.enumerated() {
        if index == listSegmentedControl.selectedSegmentIndex {
            view.tintColor = UIColor(patternImage: gradientImage)
        } else {
            view.tintColor = UIColor.gray //Whatever the color of non selected segment controller tab
        }
    }

Though looks like a ugly hack, I have been using it from a quite a while and seems fairly straight forward. Hope it helps.

EDIT:

Is this what you need buddy?

If yes lemme know, Ill post the code for the same.

EDIT 2:

As OP has mentioned in his comment that the output he is expecting is same as the one I showed in image above, providing code for the same.

Disclaimer:

As mentioned by rmaddy in his comments below, this is a hack and makes use of undocumented (Complete public API though) but a very well known hack to change the tint color of UISegemntedControl that exists from as far as iOS 5 (Thats how I remember, lemme know if I am wrong )

So use answer with the caution in mind that, in future releases of iOS Apple might change the structure of subviews in UISegemntedControl and might affect your O/P. Nothing that I can see, will result in crash but might affect the way O/P is rendered on screen.

I have declared a variable so that GradientImage can be generated only once, but its up to your implementation to use it the way you want

var gradientImage : UIImage! = nil

In ViewDidLoad I initialize the gradientImage and UISegmentedControl as

override func viewDidLoad() {
        super.viewDidLoad()
        gradientImage = gradient(size: segmentControl.frame.size, color: [UIColor.black, UIColor.red])!

        //I have specified custom font need not necessarily be used
        //Font color attribute is important though, usually `UISegementedControl` title takes color from tint color, because we might need a different color for text to highlight above gradient color am using custom font colors

        let font = UIFont(name: "HelveticaNeue-Medium", size: 20)
        segmentControl.setTitleTextAttributes([NSFontAttributeName : font!, NSForegroundColorAttributeName : UIColor.blue], for: .normal)
        segmentControl.setTitleTextAttributes([NSForegroundColorAttributeName : UIColor.white], for: .selected)

        //Set the border color and border to `UISegmentedControl` and also make it round corner

        segmentControl.layer.borderColor = UIColor(patternImage: gradientImage).cgColor
        segmentControl.layer.borderWidth = 2
        segmentControl.layer.masksToBounds = true
        segmentControl.layer.cornerRadius = 10

        //In order to update the selected Segment tint and background color we need to call multiple statements every time selection changes hence I have moved it to the function and called it in viewDidLoad

        updateGradientBackground()
    }

Finally updateGradientBackground function definition is same as the one I posted in my original answer

fileprivate func updateGradientBackground() {
        let sortedViews = segmentControl.subviews.sorted( by: { $0.frame.origin.x < $1.frame.origin.x } )
        for (index, view) in sortedViews.enumerated() {
            if index == segmentControl.selectedSegmentIndex {
                //very important thing to notice here is because tint color was not honoring the `UIColor(patternImage` I rather used `backgroundColor` to create the effect and set clear color as clear color
                view.backgroundColor = UIColor(patternImage: self.gradientImage)
                view.tintColor = UIColor.clear
            } else {
                //very important thing to notice here is because tint color was not honoring the `UIColor(patternImage` I rather used `backgroundColor` to create the effect and set clear color as clear color
                view.backgroundColor = UIColor.white //Whatever the color of non selected segment controller tab
                view.tintColor = UIColor.clear
            }
        }
    }

Finally, in IBAction of UISegmentedControl, simply call

@IBAction func segmentControllerTapped(_ sender: UISegmentedControl) {
    self.updateGradientBackground()
}

Hope this helps