assumeIsolated(_:file:line:)

Declaration

nonisolated func assumeIsolated<T>(_ operation: (isolated Self) throws -> T, file: StaticString = #fileID, line: UInt = #line) rethrows -> T where T : Sendable

Parameters

• operation:

  The operation that will be executed if the current context is executing on the actors serial executor, and the actor is a local reference.

• file:

  The file name to print if the assertion fails. The default is where this method was called.

• line:

  The line number to print if the assertion fails The default is where this method was called.

Return Value

The return value of the operation

Discussion

This method allows to assume and verify that the currently executing synchronous function is actually executing on the serial executor of the this (local) distributed actor.

If that is the case, the operation is invoked isolated to the main actor (@MainActor () -> T), allowing synchronous access to actor local state without hopping through asynchronous boundaries.

If the current context is not running on the actor’s serial executor, this method will crash with a fatal error (similar to preconditionIsolated()).

This method can only be used from synchronous functions, as asynchronous functions should instead perform a normal method call to the actor, which will hop task execution to the target actor if necessary.