What’s swift concurrency and why is it hard to use?
Generated on 7/30/2024
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Swift concurrency is a set of features in the Swift programming language designed to help developers write safe and efficient concurrent code. It includes mechanisms like actors for protecting mutable state, and the Sendable protocol for safe data sharing. The primary goal of Swift concurrency is to achieve data isolation and prevent data races, which can lead to unexpected runtime behavior, program crashes, and hard-to-reproduce issues.
Why is it hard to use?
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Data Races: Data races occur when multiple threads share data and one of them tries to mutate it. Swift concurrency aims to eliminate these by turning potential data race issues into compile-time errors, but this requires developers to adopt new patterns and practices.
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Hidden Complexity: Concurrency often introduces hidden complexity in code. For example, an app might have multiple concurrent queues for different tasks, making it difficult to track which queue is executing which code. Swift concurrency aims to simplify this by using actors and structured concurrency, but transitioning to this model can be challenging.
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Interoperability Issues: When enabling strict concurrency, developers often have to deal with other modules or libraries that haven't been updated for Swift concurrency. This can lead to warnings and errors that need to be addressed, making the migration process more complex.
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Adoption and Migration: Migrating existing code to use Swift concurrency features can be a gradual and sometimes difficult process. Developers need to understand the new concurrency model and refactor their code accordingly, which can be time-consuming and error-prone.
For more detailed information, you can refer to the sessions from WWDC 2024:
- What’s new in Swift (26:11)
- Migrate your app to Swift 6 (08:58)
Relevant Sessions
A Swift Tour: Explore Swift’s features and design
Learn the essential features and design philosophy of the Swift programming language. We’ll explore how to model data, handle errors, use protocols, write concurrent code, and more while building up a Swift package that has a library, an HTTP server, and a command line client. Whether you’re just beginning your Swift journey or have been with us from the start, this talk will help you get the most out of the language.
Migrate your app to Swift 6
Experience Swift 6 migration in action as we update an existing sample app. Learn how to migrate incrementally, module by module, and how the compiler helps you identify code that’s at risk of data races. Discover different techniques for ensuring clear isolation boundaries and eliminating concurrent access to shared mutable state.
What’s new in Swift
Join us for an update on Swift. We’ll briefly go through a history of Swift over the past decade, and show you how the community has grown through workgroups, expanded the package ecosystem, and increased platform support. We’ll introduce you to a new language mode that achieves data-race safety by default, and a language subset that lets you run Swift on highly constrained systems. We’ll also explore some language updates including noncopyable types, typed throws, and improved C++ interoperability.