Swift 6.2: Approachable Concurrency & Default Actor Isolation Issues

Understanding the coming changes and challenges.

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Swift 6.2 adds some new settings to our Swift projects, allowing us to enable Approachable Concurrency and define the Default Actor Isolation used within our projects.

These changes, once implemented, will purportedly simply our mental models of how async/await and structured concurrency works in our Swift applications.

The net effect is simple enough to understand. When both are enabled, pretty much all of your code runs on MainActor unless we explicitly indicate that we want to do otherwise.

That’s all well and good… but implementing those changes can be confusing and some of them lead to significant side-effects in our existing code bases.

This article explains and demonstrates those changes and contrasts them with how things work today. I’ll run some sample code with Approachable Concurrency and Default Actor Isolation on and off so you can see what’s going on with your own eyes.

Let’s dig in.

Approachable Concurrency

Approachable Concurrency encompasses quite a few changes under the hood, but at its core it’s designed primarily to unify how Swift…