# NSCopying A protocol that objects adopt to provide functional copies of themselves. ``` protocol NSCopying ``` ## Overview The exact meaning of “copy” can vary from class to class, but a copy must be a functionally independent object with values identical to the original at the time the copy was made. A copy produced with [`NSCopying`](/documentation/Foundation/NSCopying) is implicitly retained by the sender, who is responsible for releasing it. [`NSCopying`](/documentation/Foundation/NSCopying) declares one method, [`copy(with:)`](/documentation/Foundation/NSCopying/copy(with:)), but copying is commonly invoked with the convenience method . The method is defined for all objects inheriting from and simply invokes [`copy(with:)`](/documentation/Foundation/NSCopying/copy(with:)) with the default zone. Your options for implementing this protocol are as follows: - Implement [`NSCopying`](/documentation/Foundation/NSCopying) using and `init...` in classes that don’t inherit [`copy(with:)`](/documentation/Foundation/NSCopying/copy(with:)). - Implement [`NSCopying`](/documentation/Foundation/NSCopying) by invoking the superclass’s [`copy(with:)`](/documentation/Foundation/NSCopying/copy(with:)) when `NSCopying` behavior is inherited. If the superclass implementation might use the [`NSCopyObject`](/documentation/Foundation/NSCopyObject) function, make explicit assignments to pointer instance variables for retained objects. - Implement [`NSCopying`](/documentation/Foundation/NSCopying) by retaining the original instead of creating a new copy when the class and its contents are immutable. If a subclass inherits [`NSCopying`](/documentation/Foundation/NSCopying) from its superclass and declares additional instance variables, the subclass has to override [`copy(with:)`](/documentation/Foundation/NSCopying/copy(with:)) to properly handle its own instance variables, invoking the superclass’s implementation first. ## Topics ### Copying [`- copyWithZone:`](/documentation/Foundation/NSCopying/copy(with:)) Returns a new instance that’s a copy of the receiver. ## Relationships ### Conforming Types [`NumberFormatter`](/documentation/Foundation/NumberFormatter) [`SocketPort`](/documentation/Foundation/SocketPort) [`UnitSpeed`](/documentation/Foundation/UnitSpeed) [`Unit`](/documentation/Foundation/Unit) [`NSOrderedSet`](/documentation/Foundation/NSOrderedSet) [`NSArray`](/documentation/Foundation/NSArray) [`DateIntervalFormatter`](/documentation/Foundation/DateIntervalFormatter) [`URLSessionTask`](/documentation/Foundation/URLSessionTask) [`NSExtensionItem`](/documentation/Foundation/NSExtensionItem) [`NSUUID`](/documentation/Foundation/NSUUID) [`NSExpression`](/documentation/Foundation/NSExpression) [`NSDictionary`](/documentation/Foundation/NSDictionary) [`DateFormatter`](/documentation/Foundation/DateFormatter) [`Formatter`](/documentation/Foundation/Formatter) [`UnitArea`](/documentation/Foundation/UnitArea) [`NSURLQueryItem`](/documentation/Foundation/NSURLQueryItem) [`UnitAcceleration`](/documentation/Foundation/UnitAcceleration) [`NSUserNotificationAction`](/documentation/Foundation/NSUserNotificationAction) [`NSMutableIndexSet`](/documentation/Foundation/NSMutableIndexSet) [`UnitPower`](/documentation/Foundation/UnitPower) [`UnitPressure`](/documentation/Foundation/UnitPressure) [`URLSessionUploadTask`](/documentation/Foundation/URLSessionUploadTask) [`Scanner`](/documentation/Foundation/Scanner) [`URLSessionDataTask`](/documentation/Foundation/URLSessionDataTask) [`UnitFrequency`](/documentation/Foundation/UnitFrequency) [`NSValue`](/documentation/Foundation/NSValue) [`NSException`](/documentation/Foundation/NSException) [`NSNumber`](/documentation/Foundation/NSNumber) [`NSFileSecurity`](/documentation/Foundation/NSFileSecurity) [`NSDecimalNumber`](/documentation/Foundation/NSDecimalNumber) [`URLSessionStreamTask`](/documentation/Foundation/URLSessionStreamTask) [`NSMapTable`](/documentation/Foundation/NSMapTable) [`NSComparisonPredicate`](/documentation/Foundation/NSComparisonPredicate) [`NSMachPort`](/documentation/Foundation/NSMachPort) [`UnitDispersion`](/documentation/Foundation/UnitDispersion) [`NSPredicate`](/documentation/Foundation/NSPredicate) [`Port`](/documentation/Foundation/Port) [`UnitInformationStorage`](/documentation/Foundation/UnitInformationStorage) [`NSIndexPath`](/documentation/Foundation/NSIndexPath) [`NSAffineTransform`](/documentation/Foundation/NSAffineTransform) [`NSMeasurement`](/documentation/Foundation/NSMeasurement) [`NSCountedSet`](/documentation/Foundation/NSCountedSet) [`URLCredential`](/documentation/Foundation/URLCredential) [`NSPersonNameComponents`](/documentation/Foundation/NSPersonNameComponents) [`RelativeDateTimeFormatter`](/documentation/Foundation/RelativeDateTimeFormatter) [`UnitFuelEfficiency`](/documentation/Foundation/UnitFuelEfficiency) [`URLProtectionSpace`](/documentation/Foundation/URLProtectionSpace) [`NSURLRequest`](/documentation/Foundation/NSURLRequest) [`NSHashTable`](/documentation/Foundation/NSHashTable) [`NSSet`](/documentation/Foundation/NSSet) [`NSMutableAttributedString`](/documentation/Foundation/NSMutableAttributedString) [`ISO8601DateFormatter`](/documentation/Foundation/ISO8601DateFormatter) [`NSCalendar`](/documentation/Foundation/NSCalendar) [`NSError`](/documentation/Foundation/NSError) [`UnitDuration`](/documentation/Foundation/UnitDuration) [`MeasurementFormatter`](/documentation/Foundation/MeasurementFormatter) [`NSTimeZone`](/documentation/Foundation/NSTimeZone) [`NSURLComponents`](/documentation/Foundation/NSURLComponents) [`URLSessionConfiguration`](/documentation/Foundation/URLSessionConfiguration) [`NSItemProvider`](/documentation/Foundation/NSItemProvider) [`NSPointerFunctions`](/documentation/Foundation/NSPointerFunctions) [`UnitConcentrationMass`](/documentation/Foundation/UnitConcentrationMass) [`NSPointerArray`](/documentation/Foundation/NSPointerArray) [`NSCompoundPredicate`](/documentation/Foundation/NSCompoundPredicate) [`XMLNode`](/documentation/Foundation/XMLNode) [`XMLDocument`](/documentation/Foundation/XMLDocument) [`LengthFormatter`](/documentation/Foundation/LengthFormatter) [`ListFormatter`](/documentation/Foundation/ListFormatter) [`NSNull`](/documentation/Foundation/NSNull) [`NSURL`](/documentation/Foundation/NSURL) [`UnitVolume`](/documentation/Foundation/UnitVolume) [`NSDataDetector`](/documentation/Foundation/NSDataDetector) [`NSMutableString`](/documentation/Foundation/NSMutableString) [`NSMutableData`](/documentation/Foundation/NSMutableData) [`XMLDTDNode`](/documentation/Foundation/XMLDTDNode) [`NSMutableURLRequest`](/documentation/Foundation/NSMutableURLRequest) [`Dimension`](/documentation/Foundation/Dimension) [`NSData`](/documentation/Foundation/NSData) [`UnitMass`](/documentation/Foundation/UnitMass) [`UnitElectricCharge`](/documentation/Foundation/UnitElectricCharge) [`UnitTemperature`](/documentation/Foundation/UnitTemperature) [`URLResponse`](/documentation/Foundation/URLResponse) [`URLSessionWebSocketTask`](/documentation/Foundation/URLSessionWebSocketTask) [`NSDateComponents`](/documentation/Foundation/NSDateComponents) [`XMLElement`](/documentation/Foundation/XMLElement) [`NSRegularExpression`](/documentation/Foundation/NSRegularExpression) [`NSUserNotification`](/documentation/Foundation/NSUserNotification) [`NSMutableCharacterSet`](/documentation/Foundation/NSMutableCharacterSet) [`UnitElectricPotentialDifference`](/documentation/Foundation/UnitElectricPotentialDifference) [`URLSessionDownloadTask`](/documentation/Foundation/URLSessionDownloadTask) [`NSString`](/documentation/Foundation/NSString) [`ByteCountFormatter`](/documentation/Foundation/ByteCountFormatter) [`UnitEnergy`](/documentation/Foundation/UnitEnergy) [`EnergyKit`](/documentation/Foundation/UnitEnergy/EnergyKit) [`NSMutableDictionary`](/documentation/Foundation/NSMutableDictionary) [`UnitElectricResistance`](/documentation/Foundation/UnitElectricResistance) [`UnitIlluminance`](/documentation/Foundation/UnitIlluminance) [`NSOrthography`](/documentation/Foundation/NSOrthography) [`NSSortDescriptor`](/documentation/Foundation/NSSortDescriptor) [`UnitLength`](/documentation/Foundation/UnitLength) [`NSMutableArray`](/documentation/Foundation/NSMutableArray) [`PersonNameComponentsFormatter`](/documentation/Foundation/PersonNameComponentsFormatter) [`NSPurgeableData`](/documentation/Foundation/NSPurgeableData) [`NSLocale`](/documentation/Foundation/NSLocale) [`NSMutableOrderedSet`](/documentation/Foundation/NSMutableOrderedSet) [`DateComponentsFormatter`](/documentation/Foundation/DateComponentsFormatter) [`HTTPURLResponse`](/documentation/Foundation/HTTPURLResponse) [`NSAppleEventDescriptor`](/documentation/Foundation/NSAppleEventDescriptor) [`MassFormatter`](/documentation/Foundation/MassFormatter) [`UnitElectricCurrent`](/documentation/Foundation/UnitElectricCurrent) [`MessagePort`](/documentation/Foundation/MessagePort) [`XMLDTD`](/documentation/Foundation/XMLDTD) [`EnergyFormatter`](/documentation/Foundation/EnergyFormatter) [`UnitAngle`](/documentation/Foundation/UnitAngle) [`CachedURLResponse`](/documentation/Foundation/CachedURLResponse) [`NSIndexSet`](/documentation/Foundation/NSIndexSet) [`NSAppleScript`](/documentation/Foundation/NSAppleScript) [`NSCharacterSet`](/documentation/Foundation/NSCharacterSet) [`NSTextCheckingResult`](/documentation/Foundation/NSTextCheckingResult) [`NSDateInterval`](/documentation/Foundation/NSDateInterval) [`NSNotification`](/documentation/Foundation/NSNotification) [`NSMutableSet`](/documentation/Foundation/NSMutableSet) [`NSAttributedString`](/documentation/Foundation/NSAttributedString) [`NSDate`](/documentation/Foundation/NSDate) --- Copyright © 2026 Apple Inc. 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