A while ago I implemented my first property wrapper in a code base I work on. I implemented an @Atomic property wrapper to make access to certain properties thread-safe by synchronizing read and write access to these properties using a dispatch queue. There are a ton of examples on the web that explain these property wrappers, how they can be used and why it's awesome. To my surprise, I found out that most, if not all of these property wrappers don't actually work for types where it matters most; collection types. Let's look at an example that I tweeted about...

One of Combine's somewhat painful to work with features is its error mechanism. In Combine, publishers have an Output type and a Failure type. The Output represents the values that a publisher can emit, the Failure represents the errors that a publisher can emit. This is really convenient because you know exactly what to expect from a publisher you subscribe to. But what happens when you have a slightly more complicated setup? What happens if you want to transform a publisher's output into a new publisher but the errors of the old and new publishers don't line up? The other...

Big O notation. It's a topic that a lot of us have heard about, but most of us don't intuitively know or understand what it is. If you're reading this, you're probably a Swift developer. You might even be a pretty good developer already, or maybe you're just starting out and Big O was one of the first things you encountered while studying Swift. Regardless of your current skill level, by the end of this post, you should be able to reason about algorithms using Big O notation. Or at least I want you to understand what Big O is,...

There are several ways to initialize and configure properties in Swift. In this week's Quick Tip, I would like to briefly highlight the possibility of using closures to initialize complex properties in your structs and classes. You will learn how you can use this approach of initializing properties, and when it's useful. Let's dive in with an example right away: struct PicturesApi { private let dataPublisher: URLSession.DataTaskPublisher = { let url = URL(string: "https://mywebsite.com/pictures")! return URLSession.shared.dataTaskPublisher(for: url) }() } In this example, I create a URLSession.DataTaskPublisher object using a closure that is executed immediately when PicturesApi is instantiated. Even though...

It’s been a while since Apple announced SF Symbols at WWDC 2019 and I remember how excited everybody was about them. The prospect of having an easy to integrate set of over 1,500 icons that you can display in nine weights sounds very appealing and has helped me prototype my ideas much quicker with good looking icons than ever before. I haven’t heard or seen much content related to SF Symbols since they came out and I realized I hadn’t written about them at all so I figured that I’d give you some insight into SF Symbols and how you...

Every once in a while I run into a situation where I update my iPhone to the latest iOS before I realize I'm still using an older version of Xcode for some projects. I usually realize this when Xcode tells me that it "Could not locate device support files". I'm sure many folks run into this problem. Luckily, we can fix this by copying the device support files from the new Xcode over to the old Xcode, or by grabbing the device support files from an external source. Copying device support files if you already have the latest Xcode installed...

If you're ever amongst a group of developers and want to spark some intense discussion, all you need to do is call out that tabs are better than spaces. Or that indenting code with two spaces is much better than four. Or that the curly bracket after a function definition goes on the next line rather than on the same line as the method name. A lot of us tend to get extremely passionate about our preferred coding styles and we're not afraid to discuss it in-depth. Which is fine, but this is not the kind of discussion you and...

Sometimes you need to calculate the difference between two dates in a specific format. For instance, you might need to know the difference between dates in hours. Or maybe you want to find out how many days there are between two dates. One approach for this would be to determine the number of seconds between two dates using timeIntervalSince: let differenceInSeconds = lhs.timeIntervalSince(rhs) You could use this difference in seconds to convert to hours, minutes or any other unit you might need. But we can do better in Swift using DateComponents. Given two dates, you can get the difference in...

On iOS, you can swipe down on the home screen to access the powerful Spotlight search feature. Users can type queries in Spotlight and it will search through several areas of the system for results. You may have noticed that Spotlight includes iMessage conversations, emails, websites, and more. As an app developer, you can add content from your app to the Spotlight search index so your users can find results that exist in your app through Spotlight. An important aspect of the Spotlight index is that you can choose whether you want to index your app contents publicly, or privately....

Arrays in Swift can hold on to all kinds of data. A common desire developers have when they use arrays, is to remove duplicate values from their arrays. Doing this is, unfortunately, not trivial. Objects that you store in an array are not guaranteed to be comparable. This means that it's not always possible to determine whether two objects are the same. For example, the following model is not comparable: struct Point { let x: Int let y: Int } However, a keen eye might notice that two instances of Point could easily be compared and two points that are...