In what cases is it considered that a variable has lost its relevance and is removed from memory?

In iOS, a variable is considered to lose relevance and be eligible for deallocation from memory when there are no more strong references to it. This is managed automatically through ARC (Automatic Reference Counting).

The main cases when an object is removed from memory are:

• All strong references to the object are destroyed or set to nil.
• The object is not retained by any other object.

For example, if you have a variable that references an object, and you assign nil to it or it goes out of scope, the reference count decreases. When the count reaches zero, the object is deallocated.

class MyClass {}

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

Thus, the variable loses relevance when there are no more strong references to the object it pointed to, and the memory for the object is freed.