Concurrency

Swift Concurrency introduced one of the most important safety improvements in the language: compile-time data race detection. Before Swift Concurrency, it was possible to accidentally access mutable state from multiple threads at the same time. These bugs were notoriously difficult to reproduce because they depended on timing and thread scheduling. An application might work perfectly for months and then suddenly crash or corrupt data in production. Swift’s concurrency model takes a different approach: ...

Swift Concurrency fundamentally changed how asynchronous programming works in Swift. Before async/await arrived, developers relied heavily on completion handlers, delegates, Combine pipelines, and Grand Central Dispatch (GCD). These approaches worked, but they often made asynchronous code difficult to reason about, debug, and maintain. With Swift Concurrency, Apple introduced a model centered around tasks, structured concurrency, and actor isolation. One of the most important concepts to understand in this model is the difference between structured and unstructured concurrency. ...