# NSObjectProtocol The group of methods that are fundamental to all Objective-C objects. ``` protocol NSObjectProtocol ``` ## Overview> Note: > This protocol is imported into Swift with the name `NSObjectProtocol`. An object that conforms to this protocol can be considered a first-class object. Such an object can be asked about its: - Class, and the place of its class in the inheritance hierarchy. - Conformance to protocols. - Ability to respond to a particular message. The Cocoa root class [`NSObject`](/documentation/ObjectiveC/NSObject-swift.class) adopts this protocol, so all objects inheriting from [`NSObject`](/documentation/ObjectiveC/NSObject-swift.class) have the features described by this protocol. ## Topics ### Identifying Classes [`class`](/documentation/ObjectiveC/NSObject-c.protocol/class) Returns the class object for the receiver’s class. [`superclass`](/documentation/ObjectiveC/NSObjectProtocol/superclass) Returns the class object for the receiver’s superclass. ### Identifying and Comparing Objects [`isEqual(_:)`](/documentation/ObjectiveC/NSObjectProtocol/isEqual(_:)) Returns a Boolean value that indicates whether the receiver and a given object are equal. [`hash`](/documentation/ObjectiveC/NSObjectProtocol/hash) Returns an integer that can be used as a table address in a hash table structure. [`self()`](/documentation/ObjectiveC/NSObjectProtocol/self()) Returns the receiver. ### Testing Object Inheritance, Behavior, and Conformance [`isKind(of:)`](/documentation/ObjectiveC/NSObjectProtocol/isKind(of:)) Returns a Boolean value that indicates whether the receiver is an instance of given class or an instance of any class that inherits from that class. [`isMember(of:)`](/documentation/ObjectiveC/NSObjectProtocol/isMember(of:)) Returns a Boolean value that indicates whether the receiver is an instance of a given class. [`responds(to:)`](/documentation/ObjectiveC/NSObjectProtocol/responds(to:)) Returns a Boolean value that indicates whether the receiver implements or inherits a method that can respond to a specified message. [`conforms(to:)`](/documentation/ObjectiveC/NSObjectProtocol/conforms(to:)) Returns a Boolean value that indicates whether the receiver conforms to a given protocol. ### Describing Objects [`description`](/documentation/ObjectiveC/NSObjectProtocol/description) A textual representation of the receiver. [`debugDescription`](/documentation/ObjectiveC/NSObjectProtocol/debugDescription) A textual representation of the receiver to use with a debugger. ### Sending Messages [`perform(_:)`](/documentation/ObjectiveC/NSObjectProtocol/perform(_:)) Sends a specified message to the receiver and returns the result of the message. [`perform(_:with:)`](/documentation/ObjectiveC/NSObjectProtocol/perform(_:with:)) Sends a message to the receiver with an object as the argument. [`perform(_:with:with:)`](/documentation/ObjectiveC/NSObjectProtocol/perform(_:with:with:)) Sends a message to the receiver with two objects as arguments. ### Identifying Proxies [`isProxy()`](/documentation/ObjectiveC/NSObjectProtocol/isProxy()) Returns a Boolean value that indicates whether the receiver does not descend from [`NSObject`](/documentation/ObjectiveC/NSObject-swift.class). ### Obsolete Methods [`retain`](/documentation/ObjectiveC/NSObject-c.protocol/retain) Increments the receiver’s reference count. [`release`](/documentation/ObjectiveC/NSObject-c.protocol/release) Decrements the receiver’s reference count. [`autorelease`](/documentation/ObjectiveC/NSObject-c.protocol/autorelease) Decrements the receiver’s retain count at the end of the current autorelease pool block. [`retainCount`](/documentation/ObjectiveC/NSObject-c.protocol/retainCount) Do not use this method. [`zone`](/documentation/ObjectiveC/NSObject-c.protocol/zone) Zones are deprecated and ignored by most classes that have it as a parameter. --- 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)