Understanding the warning and how to fix it: Non-sendable cannot cross actor boundary

Question

iturrajoel OP

Created Feb ’23

Replies 5

Boosts 3

Views 5.9k

Participants 6

Hi all,

I'm testing the first beta for iOS 16.4 and Xcode 14.3 and I'm getting these warnings that I kind of understand, but I don't know and I haven't found how to solve them.

For example this code that is just a simplified example:

@MainActor class ATextModel: ObservableObject {

    @Published private(set) var record: CKRecord?

    func getData() async {
        let database = CKContainer.default().publicCloudDatabase
        let query = CKQuery(recordType: "Test", predicate: NSPredicate(value: true))

        do {
            let results = try await database.records(matching: query)
            self.record = try results.matchResults.first?.1.get()
        } catch {
            print("Error: \(error.localizedDescription)")
        }
    }
}

Is giving me 2 warnings:

Non-sendable type '(matchResults: [(CKRecord.ID, Result<CKRecord, any Error>)], queryCursor: CKQueryOperation.Cursor?)' returned by call from main actor-isolated context to non-isolated instance method 'records(matching:inZoneWith:desiredKeys:resultsLimit:)' cannot cross actor boundary

Non-sendable type 'CKQuery' exiting main actor-isolated context in call to non-isolated instance method 'records(matching:inZoneWith:desiredKeys:resultsLimit:)' cannot cross actor boundary

Does someone has a hint on how I should do this now?

This might be just an error in the beta, but I don't really think that.

Boost

Answer 1

DrMickeyLauer OP

Mar ’23

FWIW, this is a generic (as in non-Apple-specific) Swift issue that will probably find a larger audience at the official Swift forum.

0

Answer 2

SpaceMan OP

Mar ’23

I have a similar situation. I have a CKMethods protocol which I use in a number of View Controllers. I get warnings about CKRecord not being sendable. What I've been doing to try to fix it is to move the functions into the View Controllers. But now I'm stuck with this among other warnings.

let matchTemp = try await database.records(for: recIDs)

Non-sendable type '[CKRecord.ID : Result<CKRecord, any Error>]' returned by call from main actor-isolated context to non-isolated instance method 'records(for:desiredKeys:)' cannot cross actor boundary

Here's another one.

let results =  try await database.modifyRecords(saving: records, deleting: [], savePolicy: .allKeys, atomically: false)

Non-sendable type '[CKRecord]' exiting main actor-isolated context in call to non-isolated instance method 'modifyRecords(saving:deleting:savePolicy:atomically:)' cannot cross actor boundary

1

Answer 3

SpaceMan OP

Mar ’23

The issue is that CKRecord is not sendable, so the worry is that different threads could change the same CKRecord object, thus causing problems. There is a dangerous way to turn off the warnings.

extension CKRecord: @unchecked Sendable {

}

Telling the compiler to turn off the warnings. In my app, as I have mentioned before, I have a CKMethods protocol that other View Controllers use. I have never had an issue with CKRecord not being sendable before this compiler update. I am working on a new update to my app and have turned done the above dangerous move, but I welcome a solution that fixes the issue while keeping why code basically in tact.

1

Answer 4

ingconti OP

Jul ’23

same for me, and more stranger in Xcode 15 beta warning disappears... :(

0

Answer 5

Chad S. OP

Sep ’23

The reason it goes away is that Apple now makes CKRecord conform to Sendable https://developer.apple.com/documentation/cloudkit/ckrecord?changes=latest_minor

0