Blogs on Robert Harrison

Swift tip: Properly deprecating code

Fri, 18 Jul 2025 18:00:00 -0700

As codebases evolve, we inevitably accumulate functions, classes, and APIs that need to be removed or replaced. Use @available(*, deprecated, message: "...") to mark functions as deprecated in your Swift projects:

@available(*, deprecated, message: "This function will be removed in a future release.")
func oldFunction() {
    // legacy code
}

This gives developers, including your future self, a clear heads-up about upcoming changes while keeping code functional during the transition period. The compiler will show warnings but won’t break existing builds.

Swift Singleton with @unchecked Sendable

Sat, 01 Mar 2025 14:35:00 -0700

A singleton is a design pattern that ensures there is only one instance of a class. While convenient, there are drawbacks to using singletons, which are well documented elsewhere. Swift 6 provides some approaches to replacing Singletons, such as Actor. Sometimes, you run into a situation, such as re-using legacy code, where using a Singleton is preferable over refactoring to modern Swift techniques.

Pre-Swift 6, a singleton could be written like so:

Performance of SwiftUI Views with Conditional Branching

Fri, 22 Nov 2024 13:03:00 -0700

Improve the performance of your SwiftUI views by replacing if-else and switch statements with the ternary operator.

To illustrate the issue, let’s start with the following code that uses an if-else statement to set the foreground color of an image:

struct ContentView: View {
    @State private var isFavorite = true

    var body: some View {
        if isFavorite {
            Image(systemName: "star.fill")
                .foregroundStyle(Color.yellow)
        } else {
            Image(systemName: "star.fill")
                .foregroundStyle(Color.black)
        }
    }
}

The above code has two issues. First, there is some duplicate code. Second, toggling isFavorite between true and false causes SwiftUI to tear down and recreate the entire view. SwiftUI treats the if-else paths as separate Views and will do extra work to process the if and else paths. The same performance issue occurs with switch statements.

Voice Cloning using Tortoise-TTS on Apple Silicon

Sun, 17 Nov 2024 14:48:00 -0700

Voice cloning is a process that uses AI to replicate a person’s voice. The AI is trained on audio samples of a person’s voice to learn their speaking patterns. Once trained, the AI can generate speech that sounds like the original person.

Here are five practical uses of voice cloning:

Digital Assistants.
Helping people with speech disabilities.
Voiceovers in different languages.
Aid in voice acting for TV, film, commercials, and video games.
Interactive educational content.

There is a lot of power that comes with using voice cloning technology. Please use it responsibly.

Organize Code with Local Swift Packages

Wed, 25 Sep 2024 09:17:00 -0700

There are several benefits to organizing your code into modules:

Readability
Testability
Reusability
Maintainability
And more …

By using an Xcode Workspace and Swift Packages, a monolithic project can be split up and organized, into smaller modules or packages. Utilities, for example, can go in one package, and the Data Layer can go in another package.

Swift Packages can be local or remote. If the module can be used by other projects or teams, then consider using a remote package. In which case, the remote package will require its own git repository. If the module is only usable by the main application, then use a local package. The local package will live within the git repository of the main application. In this article, we’re going to use a local package.

Manage Multiple Projects with an Xcode Workspace

Mon, 23 Sep 2024 15:38:00 -0700

By default, Xcode projects use an .xcodeproj file to organize and structure the project. The project file contains code, resources, settings and targets for building a product.

What if your project needs to reference another project? For example, prior to building your main app, you must first compile and link a library. Use an Xcode Workspace (.xcworkspace) to manage the dependencies between multiple projects. Xcode can use the workspace to compile the library first, then link it to your app. If your project uses Cocoapods, then it’s using a Workspace.

SwiftUI Toggle

Tue, 22 Feb 2022 11:53:00 -0800

This article describes how to use the SwiftUI Toggle. By the end of the article you will have learned how to embed Toggle in a child View and perform the Toggle’s action in a parent View.

Let’s start with the basics. Here is a variation of the example in the official documentation:

@State private var faceIdEnabled = false
var body: some View {
    Toggle(isOn: $faceIdEnabled) {
        Text("Face ID")
    }
}

The above code will show a toggle control with “Face ID” for the title. By using a two-way binding on faceIdEnabled, we control if the toggle is on or off.

How to read data from BigQuery using Firebase Functions

Thu, 27 Jan 2022 09:00:00 -0800

An alternative title to this article could have been, “How to Access BigQuery from iOS”. I’m working on a SwiftUI app that needs to read data from BigQuery. There are several BigQuery API Client Libraries, but none are in Swift or Objective-C. There is a Node.js library. My SwiftUI app happens to use Firebase, which supports hosting Node.js code. So the decision is easy. I’ll use Node.js and Firebase.

A different approach could use the BigQuery REST API. There are couple of reasons why I chose to take the Node.js/Firebase Functions approach. (1) using a pre-built library can make development easier/quicker (2) In my use case, I want to do some data processing on the results, which makes sense to do on the backend, before returning to the frontend.

Unit Test CLLocationManager with a Mock

Mon, 10 Jun 2019 14:47:00 -0800

In this article, I’ll describe how to mock CLLocationManager, so it can be used in unit tests.

Imagine that you are building a fitness app. To track the user’s running distance, you use CLLocationManager. Instances of CLLocationManager are used to configure, start and stop Core Location services in your app.

CLLocationManager has some characteristics, which make it not very friendly to unit test. For example, calling CLLocationManager.authorizationStatus() for the first time will trigger a request for user authorization to be displayed. A unit test that is dependent on that call will fail.

8 Tips for Migrating a Salesforce Mobile SDK Project from Objective-C to Swift

Fri, 26 Apr 2019 14:43:00 -0800

Recently, I migrated parts of an iOS app from Objective-C to Swift. The app is for checking in attendees at events and uses the Salesforce Mobile SDK. I would like to share with you, some things I learned from the migration to Swift and updating to the latest Salesforce Mobile SDK.

First, the reasons (some are subjective) why I migrated parts of the app from Objective-C to Swift.

The existing Objective-C code base contained a lot of technical debt.
Salesforce Mobile SDK, which the app is tightly integrate with, is moving to Swift.
Swift is a joy to write.
Swift is easier to read.
Swift is safer to use.

Tip 1 Link to heading

Before you migrate to Swift, update your Objective-C code to modern syntax and practices. Xcode can really help you, by suggesting changes or making the changes automatically.

Salesforce Einstein ChatBot Development Process

Mon, 25 Mar 2019 14:08:00 -0800

On March 5, 2019, I participated in a Salesforce.org ChatBot Hackathon at California State University East Bay. There were participants from all over the Cal State University system, as well as the University of San Diego, which I and a colleague represented. The main objective of the event was to create intents and utterances that could be shared within the Higher-Ed community. The secondary objective was to create a chatbot using Salesforce Einstein. It was great to see the chatbots that all the groups had created. I was really impressed!