Check out my livevideo course “iOS Development with Swift in Motion”!

I’d love for you to check out my video course “iOS Development with Swift in Motion”.


The course is out on Manning’s livevideo platform, and if you get in early with Manning’s early access program you can get 40% off with code ytgrummitt at

See you in the videos!


Posted in Swift

Block comments, key bindings and feeling foolish!

Do you ever get stuck on something, and then when you work out what you were doing wrong you feel a bit foolish?

I was just thinking – it would be much more convenient if there was a keyboard shortcut to block comment some code. I know that with the keyboard shortcut Command-/ you can automatically generate single line comments:


But what I was after was a keyboard shortcut to generate block comments. Strangely this capability seems to be missing from Xcode, but I happened upon an Xcode Source Editor extension called BlockComment that seemed to do the job.

So – after installing BlockComment, I went into the Key Bindings tab in Xcode preferences, double clicked on the BlockComment binding to add a keyboard shortcut, and… nothing.BlockComment1.gif

I closed Xcode, opened Xcode – did it again and… nothing. I’ve done this before, how strange! Read up on key bindings, hmm… yes I seem to be doing the right thing, what could be going wrong?

Then I watched a video and that was when I felt foolish.

Of course! You can’t just click anywhere on the line – you need to click in the key field on the right!


Sometimes when you work out what you were doing wrong, it all seems so obvious!

So! Things I’ve learned today

FIRST – When customizing a keyboard shortcut in Key bindings – click in the Key field!

SECONDBlockComment – works quite well, I recommend!


THIRD – sometimes there’s no substitute for a video tutorial!

You might think that’s a strange sentiment for a book author, but as it turns out I’m currently working on a video course to accompany the book!

Of course, everyone has a preference for how to learn. Maybe you like books coz you can read them on the train. Maybe you prefer videos as you find it easier to learn visually. Either way, you have a choice now when learning iOS development with Swift.


You can check out the book “iOS Development with Swift” here.

Or – you can check out the livevideo course “iOS Development with Swift in Motion” here. The video course is currently in the Manning early access program, and new Units will be put out regularly.

You can use both together or independently, depending on your preference!

Good luck with them, and enjoy block commenting your code with keyboard shortcuts!

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Posted in Swift

Learn iOS and Swift – interactive video course

Exciting news! For most of this year I’ve been busy working on a series of video tutorials in iOS and Swift, and this week we’re launching the Manning Early Access Program(MEAP) for the course.

There will be 13 units in total – with approximately half an hour per unit that should be hours and hours of quality content to get you up and going in iOS and Swift.

You can check out the home for the video tutorials at Manning here, or watch a preview of the course here. To promote the launch, I have a special secret discount code ( vlgrummitt ) you can use to get 50% off, but you’ll need to move fast – it’s only valid until May 3.

You can use the video tutorials exclusively if you like, or even better – as an accompaniment to my book iOS Development with Swift, out now.

So if you’ve been thinking about learning iOS or Swift – now’s the time to dive in!



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Learn iOS Development with Swift now!

Exciting news – the book I have been working on for almost two years, iOS Development with Swift, is now done, published, printed and available on Amazon or in a bookstore near you.

The book is aimed at experienced programmers looking to migrate into developing in iOS with Swift. It assumes no previous knowledge of Swift nor iOS but skips over all the stuff you’ll already know from your experience in other languages.

After getting you up to speed on what’s new and exciting in Swift, the book takes you through building up an app from zero to App Store, exploring many different challenges you may encounter when working on an app, such as:

  • How do you deal with different devices or orientations?
  • What do you do if the keyboard pops up and covers the text field the user is editing?
  • What are different ways of navigating between scenes?
  • How do scenes communicate with each other?
  • How can you integrate animation and adaptive layout?
  • How can you handle background tasks?
  • What are the different ways of storing data locally and in iCloud?
  • What options are available for debugging in Xcode?

I’m very much looking forward to seeing the apps that readers produce after exploring iOS development with the support of the book! Do let me know about your app creations via Twitter, and I’ll post them on the website for the book.

If you’re interested in taking a peek at iOS Development with Swift, you can check it out now as a live book using Manning’s online reader.

Posted in Swift

Migrating from AS3 to Swift

As iOS 11 no longer supports 32 bit apps, I’ve been revisiting an old app that was built in Flash/ActionScript3 (and packed in 32 bit) and decided it was an opportune moment to migrate it to native iOS Xcode/Swift. Migration was quite an interesting experience, and ultimately gave me a new appreciation for Xcode/Swift, especially auto-layout, size classes, enums and type-strictness.

In general, the app looks and acts virtually identically to its predecessor. Here is the main menu for you:


But in some cases, a change was necessary. As Flash did not have access to native controls, a custom solution was used using a Starling framework called Feathers. Of course from Xcode/Swift native controls were available. I used form builder Eureka to build this up. Here’s the difference:


Charts looked a little differently too. Charts in Flash used a long-dead yahoo framework called Astra. Charts now use Daniel Gindi’s huge Charts framework, which adds some pretty cool features such as pinch to zoom and drag. Here’s the difference:


One problem that I wasn’t able to resolve was detecting data from the old version of the app in new version of the app. I couldn’t find technical information on how Air’s SharedObject was implemented, so unfortunately data has to be reset from this version. Still, better than the app simply not working!

If you’re interested in checking out the new version of the app, you can find it here.




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Migrating to Codable from NSCoding

For those who came in late: Apple introduced the `Codable` protocol in Swift 4, which allows you to encode and decode your model types to data types such as JSON and property lists, and can be used instead of the `NSCoding` protocol to archive your data.

First of all, what’s the big deal with this Codable protocol? Is it really worth the effort to learn a new approach when we already have NSCoding, that’s worked fine for years for archiving data? And if you look at a type implementing both, they are pretty similar.

Imagine we have a Product type, that contains a title, price, and quantity:

struct Product {
 var title:String
 var price:Double
 var quantity:Int

Simple model type using NSCoding

Let’s look first at how we would implement this type using NSCoding:

class Product: NSObject, NSCoding {
  var title:String
  var price:Double
  var quantity:Int
  enum Key:String {
    case title = "title"
    case price = "price"
    case quantity = "quantity"
  init(title:String,price:Double, quantity:Int) {
   self.title = title
   self.price = price
   self.quantity = quantity
  func encode(with aCoder: NSCoder) {
   aCoder.encode(title, forKey: Key.title.rawValue)
   aCoder.encode(price, forKey: Key.price.rawValue)
   aCoder.encode(quantity, forKey: Key.quantity.rawValue)
  convenience required init?(coder aDecoder: NSCoder) {
   let price = aDecoder.decodeDouble(forKey: Key.price.rawValue)
   let quantity = aDecoder.decodeInteger(forKey: Key.quantity.rawValu  e)
   guard let title = aDecoder.decodeObject(forKey: Key.title.rawValue) as? String else { return nil }

A few points:

  • We implemented the type as a class instead of a struct, as the type needs to subclass NSObject.
  • We created a Keys enum (or could have been a struct) with values are used to archive and unarchive the type’s properties.
  • We adopted the NSCoding protocol, and implemented its two required methods:
    • init which initializes the type based on decoded information from an NSCoder object.
    • encode which encodes the type into an NSCoder object.

Simple model type using Codable

Ok, now let’s look at how we could implement this type using Codable:

struct Product: Codable {
  var title:String
  var price:Double
  var quantity:Int
  enum CodingKeys: String, CodingKey {
    case title
    case price
    case quantity
  init(title:String,price:Double, quantity:Int) {
    self.title = title
    self.price = price
    self.quantity = quantity
  func encode(to encoder: Encoder) throws {
    var container = encoder.container(keyedBy: CodingKeys.self)
    try container.encode(title, forKey: .title)
    try container.encode(price, forKey: .price)
    try container.encode(quantity, forKey: .quantity)
  init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    title = try container.decode(String.self, forKey: .title)
    price = try container.decode(Double.self, forKey: .price)
    quantity = try container.decode(Int.self, forKey: .quantity)

Well, that looks familiar:

  • There is a CodingKeys enum, this time defined that describes the properties to encode.
  • The Product type adopts the Codable protocol, and implements its two required methods:
    • init which initializes the type based on decoded information from a Decoder object.
    • encode which encodes the type into an Encoder object.

Comparing Codable with NSCoding

Here’s a look at the similarities between the two approaches, in defining the model type:

Model type using Codable protocol vs using NSCoding protocol

Why use the Codable protocol?

So — if they’re so similar, why bother?

Well, there are a few good reasons:

  • You may have noticed that the Product type in the Codable example is a struct rather than a class — it doesn’t have to be, it’s just that as types that implement the Codable protocol don’t need to subclass (a reminder — NSCoding types must subclass NSObject, and therefore must be a class) they are free to be any sort of type — class, struct or even enum. The power!
  • Though I’m focusing on archiving to disk in this article, the Codable protocol isn’t just useful for archiving, it is also useful for encoding or decoding data to different data types. At the time of writing this includes JSON and property lists.
  • If it’s only encoding or decoding you’re after (for example, you might just be receiving and decoding data from a remote API), you can simply adopt the Encodable or Decodable protocols.
  • Anyone with experience with Codable is probably screaming about this advantage at the screen by now! So…the magic of the Codable protocol is that it has the power to automatically generate both of its required methods (encode and init) and the CodingKeys enum. If you’re after a straightforward encoding/decoding of Codable properties in your type, you can leave these out, and allow the compiler to auto-generate them, wow!

Model type using Codable protocol — manually specified vs generating automatically.

Why would you ever manually compose Codable functions?

Auto-generation is awesome, but there are still several circumstances where you will need to forego the convenience of auto-generation, and manually compose one or all of these. For example:

  • One or more properties of the type may not be Codable. In this case, you’ll need to convert it to and from a Codable type.
  • The structure of the type may differ from the structure you want to encode/decode.
  • You may want to encode and decode different properties than the properties of the type.
  • You may want to use different names for properties in the type.

Comparing archiving with Codable and NSCoding

We’ve seen how defining the model type compares, but how does the actual archiving of data compare?

Here is arching and unarchiving data the Product class with NSCoding:

func storeProducts() {
  let success = NSKeyedArchiver.archiveRootObject(products, toFile: productsFile.path)
  print(success ? "Successful save" : "Save Failed")
func retrieveProducts() -> [Product]? {
  return NSKeyedUnarchiver.unarchiveObject(withFile: productsFile.path) as? [Product]

And here is archiving and unarchiving our Product struct with Codable:

func storeProducts() {
  do {
    let data = try PropertyListEncoder().encode(products)
    let success = NSKeyedArchiver.archiveRootObject(data, toFile: productsFile.path)
    print(success ? "Successful save" : "Save Failed")
  } catch {
    print("Save Failed")
func retrieveProducts() -> [Product]? {
  guard let data = NSKeyedUnarchiver.unarchiveObject(withFile: productsFile.path) as? Data else { return nil }
  do {
    let products = try PropertyListDecoder().decode([Product].self, from: data)
    return products
  } catch {
    print("Retrieve Failed")
    return nil

You can see it is a little more wordy to use the Codable protocol.

This is due to two factors:

  • Encoding and decoding can throw errors with the Codable protocol. This is a good thing — it means your app is less likely to crash unexpectedly while encoding and decoding with the Codable protocol.
  • You need to manually request that your data type is encoded using a custom encoder, before passing it into be archived. (The same can be said in reverse for decoding and unarchiving.)

Migrating to Codable

So, you can see that implementing the Codable protocol vs the NSCoding protocol definitely has its benefits. The question is — what should we do with legacy projects that use NSCoding?

Well, certainly, we could do nothing. Apple hasn’t declared that they’re deprecating NSCoding, so you should be right to continue using it.

But if you do wish to update your code to the more modern Codable protocol, how…?

If we just switch our NSCoding type to a Codable type, and we run the app on a device with preexisting NSCoding data, the app won’t just fail when it tries to unarchive it as Codable data, it will crash with an NSInvalidUnarchiveOperationException. A disaster for your loyal users!

One solution is to adopt BOTH the Codable and the NSCoding protocols. The first time a legacy user uses the app, they will retrieve the data using the NSCoding protocol. Any subsequent time they save data, they will save it using the Codable protocol, and henceforth will purely be accessing their data via the Codable protocol. At some point in the distant future, you could decide to no longer support data stored using NSCoding.

Adopting both the NSCoding and Codable protocols is pretty straight-forward. Your model type that already adopts NSCoding just needs to also adopt Codable, and it will automatically synthesize Codable methods. That means, just a change to the class header: (assuming your model type doesn’t have a more complicated structure that requires manually composing Codable methods)

class Product: NSObject, Codable, NSCoding {

Retrieving data should now no longer crash if the stored data is legacy, as your Codable type also implements NSCoding and subclasses NSObject.

You will just need to update the retrieveProducts method, to handle the data regardless of whether it is encoded using NSCoding or Codable:

func retrieveProducts() -> [Product]? {
  let unarchivedData = NSKeyedUnarchiver.unarchiveObject(withFile: productsFile.path)
  //Work with Codable
  if let data = unarchivedData as? Data {
    do {
      let decoder = PropertyListDecoder()
      let products = try decoder.decode([Product].self, from: data)
      return products
    } catch {
      print("Retrieve Failed")
      return nil
  // Work with NSCoding
  else if let products = unarchivedData as? [Product] {
    return products
  } else {
    return nil

As we will store the data in Codable format regardless of how we have retrieved it, the store function shouldn’t change from how it was when storing Codable data.

That’s it! Your app should now be migrated to use Codable, and deal with any legacy NSCoding data. The next time the user saves data, they will be saving it to the Codable format.


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Posted in Swift

Migrating to Swift 4 / iOS 11

Ah, it’s migration season again, that time when all the Swifts fly to the fertile breeding grounds of version 4. 🙂

In the past, migrating your code was a big deal when a new version of Swift was introduced – when Swift 3 came around, it seemed like every line of code had a syntax change. This time around, however, life should be a lot easier on us – in fact maybe you’ll even see this nice message during your migration:

Screenshot 2017-09-12 12.26.38.png

Here’s what Chris Lattner said about it on the Accidental Tech Podcast:

I think it’s definitely fair to say that in the Swift 1 and 2 timeframes, Swift as a language was changing really rapidly, and I could see why you’d feel like you’re on uneven footing and not really sure what the language is, much less what the idioms are. Swift 3 really is quite well baked out, and I expect that going forward the new things are going to be additive, not changing the existing patterns.

That said, as you update to Xcode 9, Swift 4 and iOS 11 you might find you need to make a few little tweaks – and not just related to Swift changes. I’ve been updating all of the code base for my book, and finding there are some repetitive tasks worth mentioning:

1. Swift 3 @objc inference.

During migration, you’ll be asked if you want to minimize @objc inference (the new Swift 4 way of doing things) or handle @objc inference the Swift 3 way:
Screenshot 2017-09-12 15.30.46.png

What’s all this about?

You can tag a Swift declaration with @objc to indicate that it should be available to Objective-C. In Swift 3 many declarations were automatically inferred to be made available to Objective-C (for example methods in a subclass of NSObject were inferred to be available to Objective-C). In Swift 4, many of these are no longer going to be inferred and the migrater will help you out by adding the @objc tag in some common places it might be needed. (A common place for example, is a method that is referenced by a #selector)

For some reason, however, despite migrating your code to manage this new state of affairs, the migrater doubles down on ensuring that there are no migration problems, and sets a new ‘Swift 3 @objc inference’ setting in your targets’ Build Settings to ‘On’, ensuring that everything works just as it did in Swift 3.

This isn’t a big problem, other than increasing your app’s binary size (about 6-8% according to the swift-evolution proposal) and load time. But – if you want your app to work just like a new Swift 4 app would, change the ‘Swift 3 @objc inference’ setting in each target’s Build Settings to ‘Default’ (or ‘Off’).

Screenshot 2017-09-12 15.38.47.png

If you check out the Xcode migration guide, @objc inference is basically all it talks about. Most other Swift changes have been add-ons and non-breaking. There are however a couple of interface issues worth mentioning.

2. Safe area guides

Xcode 9 and iOS 11 introduced safe area guides, with the idea of replacing top and bottom layout guides. This change isn’t enforced by the migrator, but if you want your app to work as a new project would, you’ll want to turn on safe area guides for your storyboards.

Open a storyboard, select a view controller, and open up the file inspector. You’ll find a new check box: “Use Safe Area Layout Guides”. Check this and immediately you’ll notice a change in the document outline of your storyboard. All of your view controllers will lose their top and bottom layout guides and be replaced by safe area guides.

3. Large titles

This is another optional update, but a good idea anyway. Apple is moving towards large titles for navigation bars and has made this available to developers. To give a view controller a large title, select the first navigation bar in the navigation stack, and select ‘Prefers Large Titles’ in the attributes inspector.


This automatically sets up large titles for the whole navigation stack, though Apple suggests in many cases the large titles are more appropriate for just the initial view controller. Turn off large titles in a view controller down the line in the navigation stack, by selecting its navigation item and instead of ‘Automatic’, select ‘Never’.


4. Marketing App icon

Previously we would add the huge 1024×1024 app icons for marketing purposes in iTunesConnect. Finally, Apple has united all of the app icons, and now these app icons can also be added to your app’s assets catalog.

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