Future of concurrent code in Swift

The landscape of concurrent programming in Swift has evolved dramatically, presenting developers with multiple paths to handle complex operations.

As we stand at this technical crossroads, a crucial question emerges: which concurrency approach best serves your Swift project’s needs? More importantly, does the shift to Modern Concurrency with async/await justify the effort of refactoring your existing codebase?

In this deep dive, we’ll first step back to examine the fundamental differences between synchronous, asynchronous, and concurrent code — three distinct approaches that serve unique purposes in your application’s architecture. By understanding these core concepts, you’ll be better equipped to make informed decisions about your app’s concurrency strategy

Synchronous vs. Asynchronous vs. Concurrent Code

Let’s begin with the foundation of programming execution: synchronous code. This is the traditional and most intuitive way programs operate. Think of synchronous execution as a single-lane road where cars must travel one after another in a precise order. When your code runs synchronously, each instruction waits for the previous one to complete before beginning — like a well-orchestrated assembly line.

This picture was taken from Modern Concurrency Book by raywinderlik