Recent articles

One of Swift 5.2’s new features is the ability to use KeyPaths as functions. This can be extremely useful in cases where you’d only return the value of a certain KeyPath in a closure. Let’s look at a pre-Swift 5.2 example where this is the case: // Swift 5.1 and earlier struct User { let […]

Handling errors in Swift is done using a mechanism where functions specify their ability to throw errors. In modern Swift versions (6.0 and up), functions can even specify the type of the error that the function might throw. When we call a function that can throw, we use special syntax to either ignore the error […]

The ability to define custom subscripts in Swift is really powerful. It allows us to write very natural and concise code. Consider the following example of a Grid with a custom subscript: struct Grid { let items : [[GridItem]] subscript(x x: Int, y y: Int) -> GridItem? { guard !items.isEmpty, (items.startIndex…items.index(before: items.endIndex)).contains(x) else { return […]

A new Swift 5.2 feature is the ability to call instances of types as functions. Or, as the Swift Evolution proposal calls it “Callable values of user-defined nominal types”. The very short description of this feature is that it allows you to call instances of any type that has a callAsFunction method implemented as if […]

For years we’ve had to resort to using physical devices when testing push notifications. With Xcode 11.4, Apple finally gives developers the tools needed to test push notifications on the iOS Simulator. I’m going to assume you already know how to add push notifications to your app. If you’ve never added push notifications to an […]

So far in my Combine series I have mostly focussed on showing you how to use Combine using its built-in mechanisms. I’ve shown you how Combine’s publishers and subscribers work, how you can use Combine for networking, to drive UI updates and how you can transform a Combine publisher’s output. Knowing how to do all […]

When I just started my career as a developer there was a lot I didn’t know yet. There also were a lot of things I didn’t understand or had never done before. I have always been lucky enough to work in places where I was able to learn and grow as needed, and most importantly, […]

Oftentimes when you’re working with Combine, you’ll have publishers that produce a certain output. Sometimes this output is exactly what you need, but often the values that are output by a publisher need to be transformed or manipulated somehow before they are useful to their subscribers. The ability to do this is a huge part […]

So far in my series of posts about Combine, we have focussed on processing values and publishing them. In all of these posts, I used the sink method to subscribe to publishers and to handle their results. Today I would like to show you a different kind of built-in subscriber; assign(to:on:). This subscriber is perfect […]

In Combine, everything is considered a stream of values that are emitted over time. This means that sometimes a publisher can publish many values, and other times it publishes only a single value. And other times it errors and publishes no values at all. When your UI has to respond to changing data, or if […]