Why object is being deinitialized when ActiveReferenceCount > 0

Question

I'm reading about ARC and being confused about increasing Reference Count . My example code is below.
My first class:

class Owner{
var name: String
weak var cat:Cat? //Cat reference count will not increase because of 'weak'
init(name: String){
    self.name = name
    print("Owner class is initialized.")
  }

deinit{
    print("Owner class is deinitialized.")
  }  
}

My Second Class:

class Cat{
var name: String
var owner: Owner?

init(name: String){
    self.name = name
    print("Cat class is initialized.")
  }

deinit {
    print("Cat class is deinitilized.")
  }
}

My Class usage code:

var mamun: Owner? = Owner(name: "Mamun") //OwnerAR = 1
var vutu: Cat? = Cat(name: "Vutu") // CatAR = 1
mamun?.cat = vutu // CatAr = 1
vutu?.owner = mamun // OwnerAR = 2
mamun = nil // OwnerAR = 1
vutu = nil // CatAR = 0

Output:

Owner class is initialized.
Cat class is initialized.
Cat class is deinitilized.
Owner class is deinitialized.

Confution: When Owner reference count is 1, why it is being deinitialized after vutu = nil code execution. Am i doing wrong on counting reference?

Answer 1

When you set vutu to nil , that object's reference count goes to zero and it gets deinitialized as expected. In the process of getting deinitialized, it releases any strong references to objects it has. So its owner is released. That brings the reference count to 0 for the object referenced by your mamun variable. And that is why you see the last message of Owner class is deinitialized. .

Answer 2

mamun?.cat = vutu // CatAr = 1 (1 by vutu)

vutu?.owner = mamun // OwnerAR = 2 (1 by vutu's owner and another by mamun)

mamun = nil // OwnerAR = 1 (1 by vutu's owner) == cannot deinit until vutu deinit

vutu = nil // CatAR = 0 == vutu deinit == OwnerAR = 0 == mamun deinit