Shallow copy vs deep copy issue iOS Swift

Question

I am facing issue to clone an object in swift 3. I want to duplicate/clone an object then want to modify it's value so that modification doesn't reflect on the actual object. Here is what I did.

let patientInformation = PatientInformationController.shared().pateintInformation.copy() as! PateintInformation

patientInformation.firstName = "Some Name"

The above line actually not just modifying the local copy but also affecting the actual PatientInformationController.shared().pateintInformation.firstName The PateintInformation conforms to NSCopying protocol.

I have checked memory addresses for both objects (actual and copy), they are different.

In PatientInformation class:

required public init(instance: PateintInformation) {
    self.firstName = instance.firstName
}

public func copy(with zone: NSZone? = nil) -> Any { 
    return PateintInformation(instance: self) 
}

Answer 1

You've incorrectly implemented conformance of class to NSCopying protocol. You have same references in copy and in object, that's why changes happens. You can look here how to do it.