Mobile App

Yet Another Covid-19 App

In the past few weeks I’ve had a lot free time, and thought to myself why not another Covid-19 app? Only for Canada. You can get it from here

I tried to practice having a clean, readable and modular code. I hope I achieved these goals. Three external libraries are used in the app. CSV to decode CSV data, Charts and MBProgressHUB to show an activity indicator (I really could avoid this one and use the native one).

Data which feeds the app comes from website. The main challenge here was the input data were not consistent. From the URL to data structure. I fix the first problem I added a helper function to retrieve the file URL from an alternative when the primary function fails to fetch the file, you can getAlternativeAddress() from DeliveryManager class. To overcome to the data structure inconsistency I declared most of the columns as optional string and through two failable initializers converted them to Int and Double.

Another thing I practiced was using custom UIViews, it is a good way to modularize the code and avoid having fat view controllers.

KeyPath was another thing I used here. I guess most of us don’t care to use them, but they are really cool. Imagine you have a structure which consists of several Int type and you want to manipulate some of the numbers and show different output for different purpose. In my case I wanted to feed the chart with two different set of data, one for confirmed cases and one for number of deaths. I could create two almost identical functions to generate required data or one generic function which knew what element of the structure should be used. KeyPath was the silver bullet here:

func setChartData(data: [CSVDecodable], keyPath: KeyPath<CSVDecodable, Int>){}

Now I can call it like setChartData(data: data, keyPath: \.confirmed) or setChartData(data: data, keyPath: \.deaths) and it knows how to generate the data set.

You can download the project from

iOS: Fix label cuts for custom fonts

Has it ever occurred to you that a custom font does not look as expected in your app? like some parts of it are cut off? Look at this example, it supposed to be “Blog” but all you see is “Bl”:

Or this one in Farsi (and Arabic) which expected to be “کریم” but the last two characters are cut off completely:

The code to create it is pretty simple. I have used a third party library, FontBlaster, to load custom fonts which is available on github.

label = UILabel(frame:
let font = UIFont(name: "BleedingCowboys", size: 60)! // We are in debug mode, right?
label.backgroundColor = UIColor.yellow
label.frame.size =
label.text = "Blog"
let size = label.sizeThatFits(CGSize.init(
width: CGFloat.greatestFiniteMagnitude, 
height: CGFloat.greatestFiniteMagnitude))
label.frame.size = size =

It seems sizeThatFits(:) cannot determine the size correctly for all fonts. To fix this, I found an extension to UIBezierPath which returns a CGPath for an attributed string, you can find it here. This is how you can the path:

let line = CAShapeLayer() 
line.path = UIBezierPath(forMultilineAttributedString: mutabbleAttributedString, maxWidth: CGFloat.greatestFiniteMagnitude).cgPath
line.bounds = (line.path?.boundingBox)!
// We gonna need it later 
let sizeFromPath = CGSize(width: (line.path?.boundingBoxOfPath.width)!, height: (line.path?.boundingBoxOfPath.height)!) 

UIBezierPath(forMultilineAttributedString:, maxWidth:) comes from that extension I mentioned above. Now we can determine the actual size of the label frame, let’s see it in action:

It’s still not exactly what we want, the size seems to be correct but the left inset is not. To solve this last problem, let’s create a custom UILabel class which can set custom inset while drawing the label:

import Foundation
import UIKit

class CustomLabel: UILabel {
    var textInsets = {
        didSet { invalidateIntrinsicContentSize() }
    override func textRect(forBounds bounds: CGRect,
 limitedToNumberOfLines numberOfLines: Int) -> CGRect {
        let insetRect = bounds.inset(by: textInsets)
        let textRect = super.textRect(forBounds: insetRect, limitedToNumberOfLines: numberOfLines)
        let invertedInsets = UIEdgeInsets(top:,
                                          left: -textInsets.left,
                                          bottom: -textInsets.bottom,
                                          right: -textInsets.right)
        return textRect.inset(by: invertedInsets)
    override func drawText(in rect: CGRect) {
        super.drawText(in: rect.inset(by: textInsets))

How many points we should add to left inset? the difference between the actual width and width from sizeThatFits.First we need to replace the line in which we declared the label. Instead of the UILabel we need to use CustomLabel. Then:

label.textInsets = UIEdgeInsets(top: 0, left: sizeFromPath.width - size.width, bottom: 0, right: 0)

Let’s see the final result:

Nice! yeah? Thing is you might not need the inset for all troublesome fonts, check it yourself

iOS: Image filters using CoreImage and MetalKitView

Image filters are not only the most popular feature of image editing apps, but also in many social network apps such as Instagram, Snapchat, and Facebook Messenger. As an iOS developer, you might like to include such option into your apps.

The most convenient method would be using CIFilter create the filter and a UIImageView to show it, but there is one big problem: it’s not fast. Regarding the size of images token by iPhones (usually 12Mp), trying several image filters would not create a pleasant and “it just works” experience for the user, they don’t like to see that spinner on the screen for a simple filter, instagram does it instantly, why not your app?

For this, you need to use MetalKit instead of UIKit, which is way faster.  In this tutorial, I will create a subclass of MTKView to display a Metal drawing, filtered image in this case. It does not mean that we cannot show the final image in our lovely UIImageView.

The first step is to create a CIFilter, but before doing it let’s see what is it according to Apple:

An image processor that produces an image by manipulating one or more input images or by generating new image data. The CIFilter class produces a CIImage object as output. Typically, a filter takes one or more images as input. Some filters, however, generate an image based on other types of input parameters. The parameters of a CIFilter object are set and retrieved through the use of key-value pairs.

Let’s create a simple class to handle filters:

import Foundation
import CoreImage

enum CIFilterName: String, CaseIterable, Equatable {
    case CIPhotoEffectChrome = "CIPhotoEffectChrome"
    case CIPhotoEffectFade = "CIPhotoEffectFade"
    case CIPhotoEffectInstant = "CIPhotoEffectInstant"
    case CIPhotoEffectNoir = "CIPhotoEffectNoir"
    case CIPhotoEffectProcess = "CIPhotoEffectProcess"
    case CIPhotoEffectTonal = "CIPhotoEffectTonal"
    case CIPhotoEffectTransfer = "CIPhotoEffectTransfer"
    case CISepiaTone = "CISepiaTone"

class ImageFilters {
    private var context: CIContext
    private let image: CIImage
    init() {
        self.context = CIContext()
        self.image = CIImage()
    init(image: CIImage, context: CIContext){
        self.context = context
        self.image = image
    func apply(filterName: CIFilterName) -> CIImage?{
        let filter = CIFilter(name: filterName.rawValue)

        filter?.setValue(self.image, forKey: kCIInputImageKey)
        //filter?.setValue(Double(0.5), forKey: kCIInputIntensityKey)
        return filter?.outputImage

The above code is to create a filtered image in CIImage format using its apply() function and supports 8 filters with default settings. To use it we need to pass a CIImage and a CIContext to the initializer. 

Now we need a subsclass of MTKview which can draw a CIImage into a MTView:

import UIKit
import MetalKit
import AVFoundation

class MetalKitView: MTKView {
    private var commanQueue: MTLCommandQueue?
    private var ciContext: CIContext?
    var mtlTexture: MTLTexture?
    required init(coder: NSCoder) {
        super.init(coder: coder)
        self.isOpaque = false
        self.enableSetNeedsDisplay = true
    func render(image: CIImage, context: CIContext, device: MTLDevice) {
        #if !targetEnvironment(simulator)
        self.ciContext = context
        self.device = device
        var size = self.bounds
        size.size = self.drawableSize
        size = AVMakeRect(aspectRatio: image.extent.size, insideRect: size)
        let filteredImage = image.transformed(by: CGAffineTransform(
            scaleX: size.size.width/image.extent.size.width,
            y: size.size.height/image.extent.size.height))
        let x = -size.origin.x
        let y = -size.origin.y
        self.commanQueue = device.makeCommandQueue()
        let buffer = self.commanQueue!.makeCommandBuffer()!
        self.mtlTexture = self.currentDrawable!.texture
                               to: self.currentDrawable!.texture,
                               commandBuffer: buffer,
                               bounds: CGRect(origin:CGPoint(x:x, y:y), size:self.drawableSize),
                               colorSpace: CGColorSpaceCreateDeviceRGB())
    func getUIImage(texture: MTLTexture, context: CIContext) -> UIImage?{
        let kciOptions = [CIImageOption.colorSpace: CGColorSpaceCreateDeviceRGB(),
                          CIContextOption.outputPremultiplied: true,
                          CIContextOption.useSoftwareRenderer: false] as! [CIImageOption : Any]
        if let ciImageFromTexture = CIImage(mtlTexture: texture, options: kciOptions) {
            if let cgImage = context.createCGImage(ciImageFromTexture, from: ciImageFromTexture.extent) {
                let uiImage = UIImage(cgImage: cgImage, scale: 1.0, orientation: .downMirrored)
                return uiImage
                return nil
            return nil

Let’s talk about this new class in more details. Here and in the previous class, we have a CIContext. In both classes, it is injected into the class because it’s quite expensive operation to initiate one. Its main responsibility is compiling and running the filters, whether on CPU or GPU. Next one is a MTLCommandQueue property which, as it appears, handles queuing an ordered list of command buffers for the Metal device — has not introduced yet — to execute. The MTLCommandQueue, as well as CIContext, is thread safe and allows multiple outstanding command buffer to be encoded simultaneously. Finally, we have a MTLTexture property which is a memory allocation for storing formatted image data that is accessible to the GPU. The required init() sets two properties of our custom class, isOpaque = false tells it to do not render a black color for empty space and enableSetNeedsDisplay = true asks it to respond to setNeedsDisplay(). This class is created to render the given CIImage and here it’s done via the render() function which takes three arguments. We already know about two of them but MTLDevie is new. As you might have guessed, it defines the interface to the GPU. The body of this method makes sure there is an image to render and does a simple transform to make the image fit into the drawable area. To avoid compiler error while testing the code on a simulator, we enclose the body within #if !targetEnvironment(simulator) /// #endif, because with a simulator target the device‘s type is unknown to the compiler. The last method is obvious, it converts the formatted image to a UIImage object. 

The last step is applying a filter to a UIImage and show it on the screen:

if let device = MTLCreateSystemDefaultDevice(), let uiImage = UIImage(named: "someImage"){
    if let ciImage = CIImage(image: uiImage) {
        let context = CIContext(mtlDevice: device)
        filter = ImageFilters(image: ciImage, context: self.context)
        let ciImage = filter.apply(filterName: .CIPhotoEffectNoir)
        mtkView.render(image: ciImage, context: context, device: device)

These two classes help you to apply image filters almost instantly to images, whether small or large. 

Swift: An app to search through movie titles using The Open Movie Database API

This demo app uses OMDb APIs to search in movie titles and show details of the selected movie. First of all, you need to get your API key, it’s free. All right, this is the plan:

  • Create a class to make network requests using URLSession
  • Test the class
  • Create the UI

NetworService will handle the network requests. This is a singleton class which uses the builtin URLSession with a handful of configuration options. An extension to this class contains the required methods to search. Since I have created this as a reusable utility class, there are some extra features which won’t be used in this tutorial, maybe you need them later.

class NetworkService {
    //MARK: - Internal structs
    private struct authParameters {
        struct Keys {
            static let accept = "Accept"
            static let apiKey = "apikey"
        static let apiKey = "YOURKEY"
    //An NSCach object to cache images, if necessary
    private let cache = NSCache()
    //Default session configuration
    private let urlSessionConfig = URLSessionConfiguration.default
    //Additional headers such as authentication token, go here
    private func configSession(){
        self.urlSessionConfig.httpAdditionalHeaders = [
            AnyHashable(authParameters.Keys.accept): MIMETypes.json.rawValue
    private static var sharedInstance: NetworkService = {
        return NetworkService()
    //MARK: - Public APIs
    class func shared() -> NetworkService {
        return sharedInstance

    //MARK: - Private APIs
    private func createAuthParameters(with parameters:[String:String]) -> Data? {
        guard parameters.count > 0 else {return nil}
        return {"\($0.key)=\($0.value)"}.joined(separator: "&").data(using: .utf8)

This is the skeleton of our class, shared() function returns a static instance of the class after running the internal configSession() function. authParameters structure is used to store keys and values for authentication, just to prevent writing a messy code. Now we can create an instance of the class using, let networkService = NetworkService.shared().

Now the we need another public method to make network requests:

    private func request(url:String,
                 cachePolicy: URLRequest.CachePolicy = .reloadRevalidatingCacheData,
                 httpMethod: RequestType,
                 body: [String:String]?,
                 parameters: [URLQueryItem]?,
                 useSharedSession: Bool = false,
                 handler: @escaping (Data?, URLResponse?, Int?, Error?) -> Void){
        if var urlComponent = URLComponents(string: url) {
            urlComponent.queryItems = parameters
            var session = URLSession(configuration: urlSessionConfig)
            if useSharedSession {
                session = URLSession.shared
            if let _url = urlComponent.url {
                var request = URLRequest(url: _url)
                request.cachePolicy = cachePolicy
                request.allHTTPHeaderFields = headers
                if let _body = body {
                    request.httpBody = createAuthParameters(with: _body)
                request.httpMethod = httpMethod.rawValue
                session.dataTask(with: request) { (data, response, error) in
                    let httpResponsStatusCode = (response as? HTTPURLResponse)?.statusCode
                    handler(data, response, httpResponsStatusCode, error)
                handler(nil, nil, nil, Failure.invalidURL)
            handler(nil, nil, nil, Failure.invalidURL)

This method has the basic functionality of a request session, getting parameters and headers and returning response, data, status code and an error object if exists, asynchronously. For the httpPart, you can replace createAuthParameters(:_) with an array of URLQueryItems.

For errors, I’m using a enumerator which is inherited from Error protocol, here is it:

import Foundation
public enum Failure:Error {
    case invalidURL
    case invalidSearchParameters
    case invalidResults(String)
    case invalidStatusCode(Int?)

extension Failure: LocalizedError {
    public var errorDescription: String? {
        switch self {
        case .invalidURL:
            return NSLocalizedString("The requested URL is invalid.", comment: "")
        case .invalidSearchParameters:
            return NSLocalizedString("The URL parameters is invalid.", comment: "")
        case .invalidResults(let message):
            return NSLocalizedString(message, comment: "")
        case .invalidStatusCode(let message):
            return NSLocalizedString("Invalid HTTP status code:\(message ?? -1)", comment: "")

OMDb works with simple queries, it doesn’t have many end points! but to keep everything structured, let’s create another enumerator:

import Foundation

enum EndPoints {
    case Search

extension EndPoints {
    var path:String {
        let baseURL = ""
        struct Section {
            static let search = "/?"
        switch(self) {
        case .Search:
            return "\(baseURL)\("


The next step is testing:

import XCTest
@testable import OpenMovie

class OpenMovieTests: XCTestCase {
    private let networkService = NetworkService.shared()
    func testSearch() {
        let promise = expectation(description: "Search for batman movies") "batman", page: 1) { (searchObject, error) in
            XCTAssertTrue(searchObject?.response == "True")
        waitForExpectations(timeout: 2, handler: nil)
    func testSearchByIMDBID() {
        let promise = expectation(description: "Search for Batman: Dark Night Returns")
        networkService.getMovie(with: "tt2313197") { (movieObject, error) in
            XCTAssertTrue(movieObject?.imdbID == "tt2313197")
        waitForExpectations(timeout: 2, handler: nil)

And the results:

Now the last step, isn’t it better you look at it yourself? It’s TL;DR sort of thing, download it from github and give it a try.

This is how it looks:

iOS: Show activity indicator in UISearchBar

Updated for iOS 13 and Swift 5

When you are using a search controller, most probably it’s a network call. Isn’t it nice to show a tiny loading animation instead of the magnifier icon on the left side of the search while your app is still waiting for data from the internet? Indeed.

To do this, you can use either use private API, which is frowned upon, or use UITextField‘s built-in methodsetImage(), I go for the latter one.

First of all, let’s see how it looks:

To show the loading animation we have to:

  1. find the search bar within the search controller
  2. remove the magnifier icon
  3. add an UIActivityIndicatorView to the search bar’s leftView

And to hide it it’s almost the same steps but in reverse.

To make the code reusable, let’s do it as an extension:

import Foundation
import UIKit

extension UISearchBar {

First of all, we need to find the text field which is basically a UITextField within UISearchBar subviews. this computed property does the job for us and returns an option UItextField:

private var textField: UITextField? {
    let subViews = self.subviews.flatMap { $0.subviews }
    if #available(iOS 13, *) {
        if let _subViews = subViews.last?.subviews {
            return (_subViews.filter { $0 is UITextField }).first as? UITextField
            return nil
    } else {
        return (subViews.filter { $0 is UITextField }).first as? UITextField

The next step is finding the current magnifier image, it’s similar to the previous step:

    private var searchIcon: UIImage? {
        let subViews = subviews.flatMap { $0.subviews }
        return  ((subViews.filter { $0 is UIImageView }).first as? UIImageView)?.image

Let’s get hold of our loading animation, which is an UIActivityIndicatorView:

   private var activityIndicator: UIActivityIndicatorView? {
        return textField?.leftView?.subviews.compactMap{ $0 as? UIActivityIndicatorView }.first

Now let’s add a public variable to show/hide the loading animation:

    var isLoading: Bool {
        get {
            return activityIndicator != nil
        } set {
            let _searchIcon = searchIcon
            if newValue {
                if activityIndicator == nil {
                    let _activityIndicator = UIActivityIndicatorView(style: .gray)
                    _activityIndicator.backgroundColor = UIColor.clear
                    let clearImage = UIImage().imageWithPixelSize(size: CGSize.init(width: 14, height: 14)) ?? UIImage()
                    self.setImage(clearImage, for: .search, state: .normal)
                    textField?.leftViewMode = .always
                    let leftViewSize = CGSize.init(width: 14.0, height: 14.0)
           = CGPoint(x: leftViewSize.width/2, y: leftViewSize.height/2)
            } else {
                self.setImage(_searchIcon, for: .search, state: .normal)

This piece of code looks for an existing activity indicator and if there is none, first creates one, cleans the default image for seach mode, the magnifier image, sets a new transparent image with 14 point in 14 point in size then adds the recently created UIActivityIndicatorView to left search bar’s leftView; And to hide it, smiple removes the  UIActivityIndicatorView and set back the image for search mode.

To use it simple set searchController.searchBar.isLoading = true  but be careful if you are using it inside another block, call it withing the main queue.

You can download the whole code from github. The UIImage extension, imageWithPixelSize(), is also available on github