What happens to an object in memory if there are no active references to it anymore?

If there are no more active references to an object in memory in iOS (i.e., the reference count to the object becomes zero), the system automatically frees the memory occupied by that object. This is achieved through the automatic memory management mechanism — ARC (Automatic Reference Counting).

Example:

class MyClass {}

var obj: MyClass? = MyClass() // reference count = 1
obj = nil // reference count = 0, object is released from memory

Thus, when an object becomes unreachable, ARC deletes it, preventing memory leaks.