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:
Continue reading “Using the Swift 4.2 Timer class in Xcode 10”
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.
Continue reading “The fix to Mojave slowing down to a crawl and freezing”
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.
Continue reading “Swift 4.2: How the weirdest error message led to reimagining implicitly unwrapped optionals”
My original article — “Best Practices for Building Swift Classes” — was published on appcoda.com.
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.
Continue reading “Some best practices for designing and coding Swift classes”
My original article — “Protocol-oriented Data Structures in Swift 4: A Generic Doubly Linked List” — was published on appcoda.com.
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
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.
Continue reading “Building a generic doubly linked list using protocol-oriented Swift 4”