perform(with:completionHandler:)

Performs the action associated with the command using the information in an invocation.

Declaration

func perform(with invocation: XCSourceEditorCommandInvocation, completionHandler: @escaping  @Sendable ((any Error)?) -> Void)

func perform(with invocation: XCSourceEditorCommandInvocation) async throws

Parameters

invocation:
The invocation of the command to be invoked.
completionHandler:
A block to be executed when the command finishes.

Mentioned in

Creating a Source Editor Extension
Testing Your Source Editor Extension

Discussion

Xcode passes the code a completion handler that it must invoke to finish performing the command, passing nil on success or an error on failure. A canceled command must still call the completion handler, passing nil.

There are no guarantees about the thread or queue on which the cancellation handler is invoked.