How does Automatic Reference Counting (ARC) work at runtime?

Automatic Reference Counting (ARC) is a memory management mechanism in iOS that automatically tracks the number of references to objects during program execution. When a reference to an object is created, the counter increases, and when the reference is removed, it decreases. When the counter reaches zero, the object is automatically deallocated from memory.

Example:

class Person {
    var name: String
    init(name: String) {
        self.name = name
    }
}

var person1: Person? = Person(name: "Ivan") // counter = 1
var person2 = person1 // counter = 2
person1 = nil // counter = 1
person2 = nil // counter = 0, object is deallocated

ARC helps prevent memory leaks without the need to manually manage memory allocation and deallocation.