# protocol_addMethodDescription(_:_:_:_:_:) Adds a method to a protocol. ``` func protocol_addMethodDescription(_ proto: Protocol, _ name: Selector, _ types: UnsafePointer?, _ isRequiredMethod: Bool, _ isInstanceMethod: Bool) ``` ## Parameters `proto` The protocol you want to add a method to. `name` The name of the method you want to add. `types` A C string representing the signature of the method you want to add. `isRequiredMethod` A Boolean indicating whether the method is a required method of the `proto` protocol. If [`YES`](/documentation/ObjectiveC/YES), the method is a required method; if [`NO`](/documentation/ObjectiveC/NO), the method is an optional method. `isInstanceMethod` A Boolean indicating whether the method is an instance method. If [`YES`](/documentation/ObjectiveC/YES), the method is an instance method; if [`NO`](/documentation/ObjectiveC/NO), the method is a class method. ## Discussion To add a method to a protocol using this function, the protocol must be under construction. That is, you must add any methods to `proto` before you register it with the Objective-C runtime (via the [`objc_registerProtocol(_:)`](/documentation/ObjectiveC/objc_registerProtocol(_:)) function). --- 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)