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@@ -53,5 +53,50 @@ import Foundation
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}
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}
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}
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+
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+ /// Executes the given updateBlock and then attempts to commit the changes applied within an atomic
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+ /// transaction.
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+ ///
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+ /// The maximum number of writes allowed in a single transaction is 500, but note that each usage of
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+ /// `FieldValue.serverTimestamp()`, `FieldValue.arrayUnion()`, `FieldValue.arrayRemove()`, or
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+ /// `FieldValue.increment()` inside a transaction counts as an additional write.
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+ ///
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+ /// In the `updateBlock`, a set of reads and writes can be performed atomically using the
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+ /// `Transaction` object passed to the block. After the `updateBlock` is run, Firestore will attempt
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+ /// to apply the changes to the server. If any of the data read has been modified outside of this
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+ /// transaction since being read, then the transaction will be retried by executing the `updateBlock`
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+ /// again. If the transaction still fails after 5 retries, then the transaction will fail.
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+ ///
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+ /// Since the `updateBlock` may be executed multiple times, it should avoiding doing anything that
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+ /// would cause side effects.
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+ ///
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+ /// Any value maybe be returned from the `updateBlock`. If the transaction is successfully committed,
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+ /// then the completion block will be passed that value. The `updateBlock` also has an `NSError` out
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+ /// parameter. If this is set, then the transaction will not attempt to commit, and the given error
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+ /// will be returned.
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+ ///
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+ /// The `Transaction` object passed to the `updateBlock` contains methods for accessing documents
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+ /// and collections. Unlike other firestore access, data accessed with the transaction will not
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+ /// reflect local changes that have not been committed. For this reason, it is required that all
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+ /// reads are performed before any writes. Transactions must be performed while online. Otherwise,
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+ /// reads will fail, the final commit will fail, and this function will return an error.
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+ ///
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+ /// - Parameter updateBlock The block to execute within the transaction context.
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+ /// - Throws Throws an error if the transaction could not be committed, or if an error was explicitly specified in the `updateBlock` parameter.
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+ /// - Returns Returns the value returned in the `updateBlock` parameter if no errors occurred.
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+ func runTransaction(_ updateBlock: @escaping (Transaction, NSErrorPointer)
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+ -> Any?) async throws -> Any? {
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+ // This needs to be wrapped in order to express a nullable return value upon success.
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+ // See https://github.com/firebase/firebase-ios-sdk/issues/9426 for more details.
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+ return try await withCheckedThrowingContinuation { continuation in
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+ self.runTransaction(updateBlock) { anyValue, error in
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+ if let err = error {
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+ continuation.resume(throwing: err)
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+ } else {
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+ continuation.resume(returning: anyValue)
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+ }
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+ }
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+ }
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+ }
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}
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#endif
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Paul Beusterien