Identity Operators in Swift

In Swift, identity operators are used to check whether two objects reference the same instance in memory. These operators are useful for comparing instances of classes and ensuring that they are identical in reference, not just in value. Swift provides two identity operators:

  • ===: Returns true if two references point to the same instance.
  • !==: Returns true if two references do not point to the same instance.

Example: Using Identity Operators

In this example, we will demonstrate how the identity operators work with class instances. The program creates two separate instances of a class and compares them using identity operators to check if they refer to the same object.

File: main.swift

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class Person {
    var name: String

    init(name: String) {
        self.name = name
    }
}

let person1 = Person(name: "Alice")
let person2 = Person(name: "Alice")
let person3 = person1

// Identity comparison
print("person1 === person2: \(person1 === person2)") // false
print("person1 === person3: \(person1 === person3)") // true
print("person1 !== person2: \(person1 !== person2)") // true

Explanation:

  • person1 and person2 are two separate instances of the Person class, even though they have the same property values.
  • The identity operator === checks if two references point to the same instance. Since person1 and person2 are different instances, the comparison returns false.
  • person3 is assigned to person1, so they refer to the same instance. The comparison person1 === person3 returns true.
  • The non-identity operator !== confirms that person1 and person2 are not the same instance, returning true.

Output:

Example 1: Checking Identity in Conditional Statements

In this example, the program uses identity operators in a conditional statement to determine whether two objects are the same.

File: main.swift

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class Car {
    var model: String

    init(model: String) {
        self.model = model
    }
}

let car1 = Car(model: "Tesla Model S")
let car2 = Car(model: "Tesla Model S")
let car3 = car1

if car1 === car3 {
    print("car1 and car3 refer to the same instance.")
} else {
    print("car1 and car3 do not refer to the same instance.")
}

if car1 !== car2 {
    print("car1 and car2 refer to different instances.")
}

Explanation:

  • The program creates three Car objects: car1, car2, and car3.
  • car1 and car3 refer to the same instance, so the conditional statement prints that they refer to the same instance.
  • car1 and car2 are different instances, so the second conditional statement prints that they refer to different instances.

Output:

Conclusion

Swift’s identity operators are crucial for comparing references of class instances. They allow you to determine whether two variables point to the same object in memory, making them essential for managing object identity in your code.