Swift
Learn more and get better in Swift using this list of Swift blog posts, tutorials, tips, and tricks.
NSPredicate based XCTestExpectations for conditional checks
NSPredicate allows us to write predicates for validating a certain outcome. They're often used combined with Core Data fetch requests and require a certain knowledge for writing custom formats. Besides my earlier shared Unit tests, best practices in Xcode and Swift predicates can be useful when writing unit tests. We ...
Getting started with the Combine framework in Swift
Combine was introduced as a new framework by Apple at WWDC 2019. The framework provides a declarative Swift API for processing values over time and can be seen as a 1st party alternative to popular frameworks like RxSwift and ReactiveSwift. If you've been trying out SwiftUI, you've likely been using ...
How to test optionals in Swift with XCTest
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 ...
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 ...
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 ...
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, ...
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 ...
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 ...
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 ...
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 ...
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 ...
SwiftLee 2020 In Review: Most read blog posts
Every year I'm looking back at what I achieved with SwiftLee as well as what I want to achieve in the upcoming year. I did this in , , and I'm doing the same in this blog post for 2020. 2020 is definitely not comparable to the years before due ...