Sometimes you’ll find yourself in a situation where you want to conveniently pass some object down via the SwiftUI environment. An easy way to do this is through the .environmentObject view modifier. The one downside of this view modifier and corresponding @EnvironmentObject property wrapper is that the object you add to the environment must be an observable object. Luckily, we can extend the SwiftUI environment to add our own objects to the @Environment property wrapper without the need to make these objects observable. For example, your app might have to do some date formatting, and maybe you’re looking for a...

I’ve recently been working on a background uploading feature for an app. One of the key aspects to get right with a feature like that is to correctly handle scenarios where your app is suspended by the system due to RAM constraints or other, similar, reasons. Testing this is easily done by clearing the RAM memory on your device. Unfortunately, this isn’t straightforward. But it’s also not impossible. Note that opening the task switcher and force closing your app from there is not quite the same as forcing your app to be suspended. Or rather, it’s not the same as...

When you're working with Arrays in Swift, it's likely that you'll want to sort them at some point. In Swift, there are two ways to sort an Array: Through the Comparable implementation for each element in your array By providing a closure to perform a manual/specialized comparison between elements If you have a homogenous array of elements, for example [String], you can rely on String's implementation of Comparable to sort an array of String in some sensible manner. There are two ways to sort an array of Comparable elements: var strings = ["Oh", "Hello", "World", "This", "Is", "An", "Unsorted", "Array"]...

When you're learning about databases or multithreaded programming, it's likely that you'll come across the term "atomic" at some point. Usually you'll hear the term in the context of an operation. For example, an atomic read / write operation. Or atomic access to a property. But what does this mean? Generally, you can summarize atomic as "one at a time". For example, when accessing or mutating a property is atomic, it means that only one read or write operation can be performed at a time. If you have a program that reads a property atomically, this means that the property...

Working with dates is hard, there is no doubt about that. And formatting dates properly for every user of your app is no easier (if you want to do everything manually). Luckily, the system can help us. For example, in the US one would write "October 15" while in The Netherlands we write 15 oktober. Note that the order of the date and the month is different, the spelling of the month is different and the capitalization is different too. The DateFormatter in iOS will handle a lot of this for you. For example, if you'd use the following code...

Apple introduced SF Symbols in iOS 13. SF Symbols allow developers to easily integrate icons in their apps. The SF Symbols icons integrate really well with the default system font, and provide a consistent look throughout the system. In iOS 14, Apple added over 750 new icons to the SF Symbols library for developers to use in their apps. Additionally, Apple has expanded SF Symbols to include multi-colored icons. For a full overview of the available SF Symbols that are available, including the newly added and multicolor symbols, download the SF Symbols 2 app from Apple's SF Symbols page. To...

A Double and Float are both used to represent decimal numbers, but they do so in slightly different ways. If you initialize a decimal number in Swift using as shown below, the Swift compiler will assume that you meant to create a Double: let val = 3.123 // val is inferred to be Double The reason for this is that Double is the more precise type when comparing it to Float. A Float holds a total of 8 positions, or 32 bits. Since Double is more precise, it can hold more positions. It uses 64 bits to do this. In...

There are several ways to handle errors in Combine. Most commonly you will either use catch or replaceError if you want to implement a mechanism that allows you to recover from an error. For example, catch is useful if you want to retry a network operation with a delay. The catch and replaceError operators look very similar at first glance. They are both executed when an error occurs in your pipeline, and they allow you to recover from an error. However, their purposes are very different. When to use catch The catch operator is used if you want to inspect...

After using a MacBook that runs Xcode for a few years it's likely that your disk space is starting to fill up good. A large part of this disk space can be occupied by Device Support files that are used by Xcode for older iOS versions, or by iOS simulators that are no longer available on your machine. To clean these files up you can do the following: Go to your Terminal and type open ~/Library/Developer/Xcode/iOS\ DeviceSupport Delete folders for iOS versions that you no longer need to support. Do the same with open ~/Library/Developer/Xcode/watchOS\ DeviceSupport Clean up unavailable simulators...

Sometimes you'll want to test whether your app works properly under poor networking conditions. One way to test this is Apple's Network Link Conditioner. Unfortunately, this will slow internet speeds for your entire machine to a crawl which can be counterproductive. Especially if you want to throttle your app for a longer period of time. If you have Charles installed to debug your app's network traffic, you can use it to throttle network speeds for the entire system, or for a selection of hosts which is exactly what we're looking for. To enable throttling in Charles you can either go...