# setInterface(_:for:argumentIndex:ofReply:) Configures a specific parameter of a method to be sent as a proxy object instead of copied. ``` func setInterface(_ ifc: NSXPCInterface, for sel: Selector, argumentIndex arg: Int, ofReply: Bool) ``` ## Parameters `ifc` The [`NSXPCInterface`](/documentation/Foundation/NSXPCInterface) object that describes the protocol for the proxy object. The interface is configured the same way as the interface for an exported object or remote object proxy. `sel` Specifies which method in the protocol is being configured. `arg` Specifies the position (starting at index 0) of the parameter for which you are configuring a proxy object. This may be either the position of a parameter in the method itself or the position in its reply block. This argument must be an object. `ofReply` Pass if `arg` is an index into the parameters of the reply block, or if it is an index into the parameters of the method itself. ## Discussion If an argument to a method in your protocol should be sent as a proxy object instead of by copy, then configure the interface for that protocol with a new interface for a specific argument. An example of an object that should be a proxy instead of being copied is a view object. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)