Star rating control is the code behind a custom view to produce a number of stars that respond to touch. The stars become highlighted when touched and change a rating property.

StarRatingControl.swift

//
//  StarRatingControl.swift
//  ths
//
//  Created by Tommie Carter on 7/13/15.
//  Copyright © 2015 MING Technology. All rights reserved.
//

import UIKit

protocol StarRatingDelegate {
    func starRatingControl(control:StarRatingControl, didUpdateRating:Float)
    func starRatingControl(control:StarRatingControl, willUpdateRating:Float)
}

class StarRatingControl: UIControl {

    let kDefaultNumberOfStars = 5
    let kStarPadding:Float = 5.0

    var delegate:StarRatingDelegate!
    var rating:Float! {
        set {
            currentIdx = Int(round(self.rating))
            for (idx, _star) in stars!.enumerate() {

                (_star as! UIImageView
                    ).highlighted = (idx < currentIdx)
            }
        }
        get {
            return Float (currentIdx)
        }
    }
    var star:UIImage!
    var highlightedStar:UIImage!
    var currentIdx:Int!
    var numberOfStars:Int!
    var stars:[AnyObject]?

    //MARK: View Initialization
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.numberOfStars = kDefaultNumberOfStars
        setupView()
    }

    convenience init(frame: CGRect, numberOfStars:Int) {
        self.init(frame: frame)
        self.numberOfStars = kDefaultNumberOfStars
        setupView()
    }

    required init?(coder aDecoder: NSCoder) {

        super.init(coder: aDecoder)
        self.numberOfStars = kDefaultNumberOfStars
        setupView()

    }

    //MARK: View Layout
    func setupView () {
        self.clipsToBounds = true
        currentIdx = -1

        //let normal = UIImage.imageFromText("★", fontname: "Chalkduster", fontSize: CGFloat(60.0))?.imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)
        //let highlightedImage = UIImage.imageFromText("★", fontname: "Chalkduster", fontSize: CGFloat(60.0))?.imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)

        star = UIImage.imageFromText("★", fontname: "Chalkduster", fontSize: CGFloat(60.0))?.imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)

        //UIImage(named:  "star.png")
        highlightedStar = UIImage.imageFromText("★", fontname: "Chalkduster", fontSize: CGFloat(60.0))?.imageWithRenderingMode(UIImageRenderingMode.AlwaysTemplate)


        var s = Array<AnyObject>()
        s.reserveCapacity(self.numberOfStars)
        for (var i = 0; i < numberOfStars; i = i + 1) {

            let v = UIImageView(image: star, highlightedImage: highlightedStar)
            v.tintColor = UIColor.yellowColor()
            self.addSubview(v)
            s.append(v)
        }
        stars = s
    }
    /*
    // Only override drawRect: if you perform custom drawing.
    // An empty implementation adversely affects performance during animation.
    override func drawRect(rect: CGRect) {
        // Drawing code
    }
    */

    override func layoutSubviews() {
        super.layoutSubviews()

        let width = CGFloat((Float(self.frame.size.width) - (kStarPadding * Float(numberOfStars + 1))) / Float(numberOfStars))

        let cellWidth = min(self.frame.size.height, width)

        // We need to align the stars in the center of the view
        let totalCellWidth = (Float(self.frame.size.width) - (Float(cellWidth) * Float(numberOfStars)))
        let padding = totalCellWidth + (kStarPadding * (Float(numberOfStars) + 1)) / Float(2.0)

        for (idx, _star) in stars!.enumerate() {
            let paddedValue = padding + kStarPadding + Float(idx) * Float(cellWidth) + Float(idx) * kStarPadding

            let frame = CGRectMake(CGFloat(paddedValue) * CGFloat(kStarPadding), 0, cellWidth, cellWidth)

            (_star as! UIImageView
                ).frame = frame
        }
    }

    func starForPoint(point:CGPoint) -> UIImageView? {
        for star in stars! {
            if let imageView = star as? UIImageView {
                (CGRectContainsPoint(star.frame, point))
                return imageView
            }
        }

        return nil
    }

    func indexForStar(atPoint:CGPoint) -> Int {

       let _stars = stars as! [UIImageView]
        return _stars.indexOf(self.starForPoint(atPoint)!)!
    }

    //MARK: Touch Events
    override func beginTrackingWithTouch(touch: UITouch, withEvent event: UIEvent?) -> Bool {

        //super.beginTrackingWithTouch(touch, withEvent: event)

        let _star = stars![0] as! UIImageView

        let point = touch.locationInView(self)
        let index = self.indexForStar(point)
        if (index != NSNotFound) {
            self.rating = Float ( index+1 )
            //if (self.delegate?.starRatingControl:willUpdateRating) ///{

            let pointOffset = Int(point.x)
            let firstStarPoint = Int ( _star.frame.origin.x )


            if ( pointOffset < firstStarPoint ) {

                self.delegate.starRatingControl(self, willUpdateRating: self.rating)

            } else {
                self.rating = 0
                self.delegate.starRatingControl(self, willUpdateRating:self.rating)
            }
        }
        
        return true
    }

    override func cancelTrackingWithEvent(event: UIEvent?) {
        super.cancelTrackingWithEvent(event)
    }

    override func continueTrackingWithTouch(touch: UITouch, withEvent event: UIEvent?) -> Bool {
        let point = touch.locationInView(self)
        let index = self.indexForStar(point)
        let _star = stars![0] as! UIImageView

        if (index != NSNotFound) {
            self.rating = Float( index + 1 )

            let pointOffset = Int(point.x)
            let firstStarPoint = Int ( _star.frame.origin.x )


            if ( pointOffset < firstStarPoint ) {

                self.delegate.starRatingControl(self, willUpdateRating: self.rating)

            } else {
                self.rating = 0
                self.delegate.starRatingControl(self, willUpdateRating:self.rating)
            }
        }
        return true


    }

    override func endTrackingWithTouch(touch: UITouch?, withEvent event: UIEvent?) {

        self.delegate.starRatingControl(self, didUpdateRating: self.rating)

        super.endTrackingWithTouch(touch, withEvent: event)

    }


}