Let's take a look at what's changing…
- Tip: You can also download this as an Xcode playground if you want to try the code samples yourself.
Data races are now clearly diagnosed
Swift concurrency was introduced back in Swift 5.5, but had a bit of a rocky adoption both in Apple's own frameworks and our own projects. However, with Swift 5.10 the team made a rather dramatic statement: "Swift 5.10 closes all known static data-race safety holes in complete strict concurrency checking."Concurrency checking is what allows the compiler to verify our use of concurrent code is safe – that we aren't accidentally sharing mutable state in a way that can cause race conditions. Of course, the key word here is "known": everything they know about has been resolved.
Apple's work here is not only hugely innovative, but hugely complex: similar to how type inference requires the Swift compiler to be able to reason about how various parts of our code are used, in concurrency the compiler is effectively running a series of algorithms that attempt to determine conclusively that our code is concurrency-safe.
To give you a concrete example, this code generated a warning in Swift 5.9:
import SwiftUI
struct ContentView: View {
var body: some View {
Button("Tap Me", action: doWork)
}
func doWork() {
print("Hello")
}
}The problem here is that SwiftUI's
Button view doesn't use @MainActor for its action, so Swift was throwing up a warning that we were calling a main acto...https://www.hackingwithswift.com/articles/267/whats-new-in-swift-5-10
