Why is the struct type UUID not sendable?

Question

Given that type UUID is a struct I thought it would be Sendable. But the compiler generates a warning:

struct S: Sendable {
	var int: Int
	var id: UUID // <-- Stored property 'id' of 'Sendable'-conforming struct 'S' has non-sendable type 'UUID'
}

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Posted by

peggers123

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Answer 1

UUID does not conform to Sendable (even though it is a struct, but some of its components may be mutable ?) Conforms to:

CustomReflectable
CustomStringConvertible
Decodable
Encodable
Equatable
Hashable
ReferenceConvertible

Hence, S does not conform either.

See example in Proposal: SE-0302 https://github.com/apple/swift-evolution/blob/main/proposals/0302-concurrent-value-and-concurrent-closures.md

// error: MyNSPerson cannot conform to Sendable due to NSMutableString member.
// note: add '@unchecked' if you know what you're doing.
struct MyNSPerson : Sendable {
  var name: NSMutableString
  var age: Int
}

Posted by

Claude31

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Answer 2

So, I want to draw your attention to this quote from Concurrency in Swift 5 and 6:

This allows Sendable conformances to be built up throughout the ecosystem without blocking incremental adoption on a bottom-up process.

Adding Sendable conformances to library types — both built-in stuff like UUID and third-party libraries — is part of that “incremental adoption” process.

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—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Posted by

eskimo

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Answer 3

To bump an old thread... UUID is now Sendable!

https://developer.apple.com/documentation/foundation/uuid/

Posted by

tim_the_bear

Yep. And thanks for the update.

—
eskimo

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Why is the struct type UUID not sendable?

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