Optionals types in Swift either have a value or not, and there are several ways to test optionals using the XCTest framework. APIs like XCTUnwrap are designed to unwrap an optional and throw an error if unwrapping failed. However, it can easily lead to writing many unwraps before evaluating the actual outcome you want to …
How to use the rethrows keyword in Swift
Rethrows in Swift allows forwarding a thrown error by a given function parameter. It’s used a lot in methods like map, filter, and forEach and helps the compiler to determine whether or not a try prefix is needed. In my experience, you don’t have to write rethrowing methods that often. However, once you know how …
How to use @autoclosure in Swift to improve performance
@autoclosure in Swift is a type of closure that allows to omit braces and make it look like a normal expression. Under the hood, however, it’s still a closure. By understanding what this means, we can improve the efficiency of our code. The @autoclosure keyword might be new to you. For many of us, it’s …
How to create a Dynamic Pager View for onboardings
A pager view in SwiftUI like we know UIPageViewController in UIKit didn’t exist until iOS 14 and macOS 11.0. Using the PageTabViewStyle on a TabView will result in a swipeable set of pages. However, what if you want to support iOS 13? And how would you do something similar on macOS Catalina? On top of …
How and when to use Lazy Collections in Swift
Lazy collections are similar to a regular collection but change the way how modifiers like map, filter, and reduce are processed. In my experience, they haven’t got as much attention as they should as they can be more performant in certain cases. You might be more familiar with lazy vars, but have you used the …
How to use Variadic parameters in Swift
Variadic parameters make it possible to pass zero or more values of a specific type into a function. It can be a clean alternative for methods that often work with one element, and you don’t want to create an array of components for just a single value on the implementation level. The great thing about …
XCTExpectFailure: Expected test failures explained with code examples
XCTExpectFailure was introduced in Xcode 12.5 and allows marking test failures as expected. The first time I read about this new API I was kind of confused: why wouldn’t we use methods like XCTAssertThrowsError instead? I continued my journey and quickly realised this API is a welcome addition to the XCTest framework. In fact, it …
Lazy var in Swift explained with code examples
A lazy var is a property whose initial value is not calculated until the first time it’s called. It’s part of a family of properties in which we have constant properties, computed properties, and mutable properties. A lazy property might be lesser known to beginners in Swift but are actually super valuable once you know …
Closures in Swift explained with Code Examples
Closures in Swift can be challenging to understand with types like trailing closures, capturing lists, and shorthand syntaxes. They’re used throughout the standard library and are part of the basics you need to know when writing Swift code. Xcode will help us most of the time with the right syntax using autocompletion but it’s good …
What is a Computed Property in Swift?
Computed properties are part of a family of property types in Swift. Stored properties are the most common which save and return a stored value whereas computed ones are a bit different. A computed property, it’s all in the name, computes its property upon request. It can be a valuable addition to any of your …