When you write the compiler quietly sets a lot of machinery in motion. Usually writing a for loop is a pretty mundane task, it’s not that complex of a syntax to…

Donny Wals's blog offers insights into iOS development, Swift programming, and software engineering best practices. Readers can explore articles covering topics such as SwiftUI, Combine framework, and iOS app architecture patterns. Additionally, they can learn about iOS app testing, debugging techniques, and publishing apps on the App Store.

Donny Wals

Explores how Swift's iteration machinery works under the hood, from the basic Sequence and Collection protocols to their async counterparts. Explains how for-in loops desugar into iterator calls, why most iterators are structs with value semantics, and the pitfalls of mutating collections during iteration. Includes practical examples of implementing custom sequences and collections, plus guidance on bridging callback-based APIs to async streams using AsyncSequence.

A deep dive into Collections, Sequences, and Iterators in Swift – Donny Wals