Using Xcode 10 Instrument’s Time Profiler template to optimize Swift 4.2 code

My original article — “How to Use Xcode Instrument to Optimize Your Swift Code” — was published on

I still run across curmudgeons who flat out reject techniques like object-oriented programming (especially inheritance and polymorphism), protocols and protocol-oriented programming (especially composition), generics, and closures. On a conscious level, the curmudgeons usually reject these technique because of their supposed “massive” performance cost. On a subconscious level, the curmudgeons don’t understand these technologies. So do we give up all hope or do we accept the fact that compiler designers have come up with brilliant optimizations that ameliorate the use of such high-level technologies? We believe in Swift’s compiler designers. Do we realize that there are great tools like Xcode Instruments that help us find awkward implementations of these techniques and give us the opportunity to come up with our own optimizations? Yes.

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Dividing and conquering your Xcode projects with targets

My original article — “Dividing and Conquering Your Xcode Projects with Targets” — was published on

In this tutorial, I’ll show you how to leverage Xcode targets to control the massive complexity involved in building iOS (and macOS, watchOS, and tvOS) apps. A lot of time can be saved when developers realize that not everything they’re required to do has to be done by writing software language code, like Swift. Integrated development environments (IDEs) like Xcode offer very powerful tools, like targets, that allow developers to decouple nitty-gritty tasks that used to be done in code (or manually) out into project configuration settings. I’ve found that, because of the sheer number of project settings, developers often take one look at say, Xcode’s long, long list of Build Settings, and want to curl up and pass out. When finished reading this tutorial, you’ll see that you can neatly organize code into one project that’s capable of producing binaries for iOS, macOS, watchOS, and tvOS.

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Using the Swift 4.2 Timer class in Xcode 10

Developers often need to do something many times and at regular intervals. One common application of such a use case is checking some process’s or device’s status, a technique called “polling.” In this tutorial, I’ll show you how to use the Swift 4.2 Timer class in Xcode 10 to repeatedly perform a simple task, every second, for 1 minute (60 seconds) — and update the user interface (UI) on each “tick.” You’ll learn how to start a timer ticking, pause it, resume it, stop it, and do something on each tick. Here’s what we’ll create during this tutorial — and the source code is available for download from GitHub:

To emphasize that the UI remains responsive when a timer is used judiciously, I added a UISlider to my storyboard and tested my code. Here’s the result:

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The fix to Mojave slowing down to a crawl and freezing

If you’re one of the brave people who’ve installed Apple’s new Mojave (macOS 10.14) operating system, you may be experiencing extreme sluggishness and steady slowdowns after boot until everything just freezes up and you can’t do anything. It’s really exasperating, but there’s a cure for the freeze-ups… If your Mac’s primary drive has multiple partitions, and/or you have an external drive attached, and/or your external drive has multiple partitions.

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Swift 4.2: How the weirdest error message led to reimagining implicitly unwrapped optionals

In this tutorial, I’ll show you how researching and learning about the current programming language you’re using (i.e., Swift) can lead you to new discoveries, a better understanding of the language, and becoming a better problem solver. Recently, I ran into a Swift error that at first had me scratching my head. The error had to do with implicitly unwrapped optionals. My debugging and contemporaneous research led me to the little-known fact that, in Swift 4.2, a proposal “to remove the ImplicitlyUnwrappedOptional type from the Swift type system and replace it with an IUO attribute on declarations” was accepted and implemented. Despite the fact that I followed and covered language changes leading to Swift 4.2, I missed this seemingly innocuous but nonetheless prescient modification.

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Some best practices for designing and coding Swift classes

My original article — “Best Practices for Building Swift Classes” — was published on

Follow along as I write this tutorial’s Swift code in a playground! Download from GitHub.

In this tutorial, I’m going to show you some best practices that will help you design and implement classes (reference types) and then safely leverage reference semantics in Swift. Protocol-oriented programming (POP) and value semantics are all the rage now, but a promising new technology doesn’t mean you should throw all your classes away. Why not add some simple constructs to your classes like copy initializers, default initializers, designated initializers, failable initializers, deinitializers, and conformance to the Equatable protocol? To get real about my sample code, I’ll adopt these constructs in some classes and show you my best practices working in real life for drawing in your iOS app interfaces.

I’ll walk through the process of creating several protocols, creating classes that adopt those protocols, implement inheritance in these classes, and use instances of the classes (objects), all to illustrate my best practices — and to show some of the extra steps you may have to go through when working with classes.

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Building a generic doubly linked list using protocol-oriented Swift 4

My original article — “Protocol-oriented Data Structures in Swift 4: A Generic Doubly Linked List” — was published on

Follow along with this tutorial! Download the Swift 4 code from GitHub.

Let’s talk about creating a list on steroids, i.e., a generic doubly linked list in Swift. For our purposes here, a list is a software receptacle that contains related data that we’re interested in inspecting, organizing, manipulating, etc. A doubly linked list stores a list of “nodes.” Each node contains data, knows about the preceding node in the list, and knows about the following node in the list. We’ll talk about adding nodes to the list, removing nodes from the list, displaying information stored in nodes in the list, and traversing the list. I’ve used the term generic because you’ll see that I can store store pretty much every built-in or custom Swift type in my linked list, like Double, UINavigationController, Int, CGFloat, UIView, CGAffineTransform… You can even store a collection of instances of a custom class or struct in my list (see section “Storing custom types” below). Most importantly, I’ll show you how to move towards generic programming, also known as generics, parametric polymorphism, templates, or parameterized types, where, when possible, we can write code that applies to many types, and thus reduces code redundancy.

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Self versus self in Swift 4 – capital “S” and lowercase “s”

RELATED: Find out how to make a copy of a class instance (object) using a C++-like copy constructor — a copy initializer in Swift.

Those of you who’ve used Objective-C and Swift for any meaningful length of time must be familiar with the self property of structs and classes. I’m not sure how many are aware of the Self “type” (sometimes called a “requirement”). I would be very interested in knowing how many understand the difference between self and Self. I’m talking about self with lower-case “s,” which I’ll call “small self” herein. It’s pretty well documented. Similarly, Self with an upper-case “S,” is what I’ll call “tall self” herein. It’s not very well documented.

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Class copy constructors in Swift 4 for defensive copying

Swift tutorials by Notice that Swift almost seems to frown on making a copy of a reference type, i.e., a copy of an instance of a class, or, as some would rather put it, getting a copy of an object. I’m not talking about getting another reference to a class, I’m talking about getting an entire, separate copy of a class instance. This frowning on class copying is not an accident. Swift’s language architects want the syntax and semantics of the language to be crystal clear. They want developers to be confident that reference types and value types will both have 1) distinct and obvious meanings and that both types will 2) behave consistently. But still, why not be able to safely make a copy of a class instance? I’ll show you how in this tutorial by borrowing the copy constructor concept from C++. In Swift, we’d call this a “copy initializer.” (NOTE: Yeah, yeah, yeah, I know about NSCopying in Cocoa and Objective-C.)

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