# protocol_addProperty(_:_:_:_:_:_:) Adds a property to a protocol that is under construction. ``` func protocol_addProperty(_ proto: Protocol, _ name: UnsafePointer, _ attributes: UnsafePointer?, _ attributeCount: UInt32, _ isRequiredProperty: Bool, _ isInstanceProperty: Bool) ``` ## Parameters `proto` The protocol you want to add a property to. `name` The name of the property you want to add. `attributes` An array of property attributes. `attributeCount` The number of properties in `attributes`. `isRequiredProperty` A Boolean indicating whether the property’s accessor methods are required methods of the `proto` protocol. If [`YES`](/documentation/ObjectiveC/YES), the property’s accessor methods are required methods; if [`NO`](/documentation/ObjectiveC/NO), the property’s accessor methods are optional methods. `isInstanceProperty` A Boolean indicating whether the property’s accessor methods are instance methods. If [`YES`](/documentation/ObjectiveC/YES), the property’s accessor methods are instance methods. [`YES`](/documentation/ObjectiveC/YES) is the only value allowed for a property. As a result, if you set this value to [`NO`](/documentation/ObjectiveC/NO), the property will not be added to the protocol. ## Discussion The protocol you want to add the property to must be under construction—allocated but not yet registered 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)