show scratch-card effect with the help of using scratch and win example

Question

I am new in ios developement.i need to show scratch-card effect for an iPhone app after scratches if coupon number is visible i need to show alert message How can i do this?.i

Answer 1

A simple UIImageView subclass that allows your UIImageView become a scratch card.

In your storyboard or xib set custom class of your UIImageView that represents your scratch image to ScratchCardImageView. Change lineType or lineWidth to change the appearance of the scratch lines.

Download example

Swift 3:

import UIKit


class ScratchCardImageView: UIImageView {

    private var lastPoint: CGPoint?

    var lineType: CGLineCap = .square
    var lineWidth: CGFloat = 20.0

    override func awakeFromNib() {
        super.awakeFromNib()

        isUserInteractionEnabled = true
    }

    override func touchesBegan(_ touches: Set, with event: UIEvent?) {

        guard  let touch = touches.first else {

            return
        }

        lastPoint = touch.location(in: self)
    }

    override func touchesMoved(_ touches: Set, with event: UIEvent?) {

        guard  let touch = touches.first, let point = lastPoint else {

            return
        }

        let currentLocation = touch.location(in: self)
        eraseBetween(fromPoint: point, currentPoint: currentLocation)

        lastPoint = currentLocation
    }

    func eraseBetween(fromPoint: CGPoint, currentPoint: CGPoint) {

        UIGraphicsBeginImageContext(self.frame.size)

        image?.draw(in: self.bounds)

        let path = CGMutablePath()
        path.move(to: fromPoint)
        path.addLine(to: currentPoint)

        let context = UIGraphicsGetCurrentContext()!
        context.setShouldAntialias(true)
        context.setLineCap(lineType)
        context.setLineWidth(lineWidth)
        context.setBlendMode(.clear)
        context.addPath(path)
        context.strokePath()

        image = UIGraphicsGetImageFromCurrentImageContext()

        UIGraphicsEndImageContext()
    }
}

Updated

With this solution touch events will be tracked only inside the UIImageView bounds. If you need touch events to start already outside your scratchcard, see ScratchCardTouchContainer example