August 2018 – iOS Brain

Fix for prohibitory symbol (do not enter, stop sign) when booting into or updating macOS Mojave 10.14 (including betas)

FLASH: Updated 11/9/22 with a tutorial on how to obtain installers for macOS Ventura 13.0 and many older macOS versions.
FLASH: Updated 10/25/18 with NEW INSIGHTS on how to deal with the prohibitory symbol. When installing the macOS Mojave 10.14 beta 11 and then the public macOS Mojave 10.14, I ran into the prohibitory symbol again, actually twice during both installations, but got through to the final install in both cases. You should read this entire article, but if you’re in a hurry, jump to the section covering working around hitting the prohibitory symbol twice.

Swift 4.2 improvements? Member/dot syntax for subscripts. Trying it out in a protocol-oriented, generic linked list.

The code shown herein will only compile and link in Xcode 10 beta and run on iOS 12 beta and/or OS X 10.14 beta.

While working on a Swift protocol-oriented and generic linked list, I got to thinking about Apple’s “improvements” to version 4.2 of their flagship language. Since a linked list is a list, I thought, “Why not add a subscript to my linked list to facilitate finding specific nodes in my list?” I did that in Swift 4.1 and got what most developers would’ve expected, e.g., used linkedList["node4"] to get the node in the list associated with the keyword “node4.” With Swift 4.2, I can use the controversial new @dynamicMemberLookup language attribute and implement dot/member notation, like linkedList.node4 to get that same node in the list associated with “node4.” Big improvement, huh? Well, maybe. We’ll talk about how this new and improved subscript is more than just about syntactic sugar, but that the “driving motivation for this feature is to improve interoperability with inherently dynamic languages like Python, Javascript, Ruby and others.” Note that all code shown in this tutorial was written in two Xcode 10 beta playgrounds.

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Xcode 9 playground error: No such module ‘UIKit’ (or ‘AppKit’)

While creating a new Xcode playground on my MacBook Pro today, I got the most bizarre error message: “No such module ‘UIKit'”. I was using Xcode Version 9.2 (9C40b). Yes, I know there are more recent versions, but I haven’t had the need to upgrade my MacBook Pro. Parenthetically, I do have Xcode 9.4.1 (9F2000) and Xcode 10 beta 6 (10L232m) loaded on my main development machine. I’ll share the solution to this problem with you in the hopes that you, like me, will learn something new about Xcode today.

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Swift 4.2 improvements: #warning and #error compiler directives

The code shown herein will only compile and link in Xcode 10 beta and run on iOS 12 beta and/or OS X 10.14 beta.

We’re in the middle of Apple’s annual product upgrade cycle and this article is the second in a series of tutorials, started last week, meant to highlight the most important new features of Swift 4.2. Today, we’ll look at two two new Swift 4.2 features, the #warning and #error compiler directives.

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Two Behavioral Design Patterns in Swift: Observer and Memento

My original article — “Design Patterns in Swift #2: Observer and Memento” — was published on appcoda.com.

This tutorial is the second installment in a series on design patterns started last week. There are 23 classic software development design patterns probably first identified, collected, and explained all in one place by the “Gang of Four” (“GoF”), Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides in their seminal book, “Design Patterns: Elements of Reusable Object-Oriented Software.” Today, we’ll focus on two of these patterns, “observer” and “memento,” which fall into what the GoF calls the “behavioral” category. Follow along with the Xcode projects, both on GitHub, available for observer here and memento here.

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Swift 4.2 improvements to Collection and Sequence protocols with method allSatisfy

The code shown herein will only compile and link in Xcode 10 beta and run in iOS 12 beta and/or OS X 10.14 beta.

We’re in the middle of Apple’s annual product upgrade cycle and this article is the first in a series of tutorials meant to highlight the most important new features of Swift 4.2. Instead of trying to cover all of the 4.2 features/improvements in one very long article, I’m going go talk about each aspect of the new 4.2 version, one or two features at a time. (If you’re interested in more details as to why I’m focused on 4.2, see section “Swift version methodology” below.) Today, I’ll cover the allSatisfy(_:) instance method (see also here) of the Sequence protocol (see also here), of course intimately related to the Collection protocol (see also here).

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Controlling chaos: Error checking in Swift 4 with if let, guard, and failable initializers

Swift tutorials by iosbrain.com In this tutorial, the third in a series of tutorials, we’re going to finish the arduous topic of looking for unexpected values, events, and conditions that arise during program execution, using a technique I like to call “error checking.” Today, I’ll concentrate on nil values, optionals, optional binding, the guard statement, failable initializers, and finally, give you some advice about keeping your error checking code consistent, for example, when to use Swift “Error Handling” or when just to return true/false or use guard statements.

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Month: August 2018