About Memory management in iOS

Memory management in iOS was initially non-ARC (Automatic Reference Counting), where we have to retain and release the objects. Now, it supports ARC and we don't have to retain and release the objects. Xcode takes care of the job automatically in compile time.

Memory management is the programming discipline of managing the life cycles of objects and freeing them when they are no longer needed.

ARC (Automatic Reference Counting)

Every time you create a new instance of a class, ARC allocates a chunk of memory to store information about that instance. This memory holds information about the type of the instance, together with the values of any stored properties associated with that instance.

Additionally, when an instance is no longer needed, ARC frees up the memory used by that instance so that the memory can be used for other purposes instead. This ensures that class instances don’t take up space in memory when they’re no longer needed.

Strong references / Weak references

Resolving Strong Reference Cycles Between Class Instances

Swift provides two ways to resolve strong reference cycles when you work with properties of class type: weak references and unowned references.

Memory safety

func balance(_ x: inout Int, _ y: inout Int) {
    let sum = x + y
    x = sum / 2
    y = sum - x
}
var playerOneScore = 42
var playerTwoScore = 30
balance(&playerOneScore, &playerTwoScore)  // OK
balance(&playerOneScore, &playerOneScore)
// Error: conflicting accesses to playerOneScore