Mastering ObjectIdentifier in Swift

Ensuring Uniqueness of Class Instances

Photo by Jessica Ruscello on Unsplash

Before we start

Difficulty: Beginner | Easy | Normal | Challenging

Keywords and Terminology:

ObjectIdentifier: A unique identifier for a class instance or metatype

Prerequisites:

• None

Why

In Swift, class instances and metatypes have unique identities (because if we make a copy, we copy a reference to a unique instance).

Usage

You might create a simple Class type that represents a person, something (for simplicity's sake) that looks like the following:

class Person: Equatable {
    static func == (lhs: Person, rhs: Person) -> Bool {
        lhs.name == rhs.name
    }
    
    var name: String
    init(_ name: String) {
        self.name = name
    }
}
let alisha = Person("Alisha")

Now we can create an identifier

let personIdentifier = ObjectIdentifier(alisha)

if we print (in this case) personIdentifier, we get a rather lovely address (and of course this is likely to differ on your machine):

print (personIdentifier) //…