How Swift Uses ARC and Deinitializers to Automatically Manage Memory

Swift classes use a system called Automatic Reference Counting (ARC) to track how many variables point to a given class instance at any time. Each new reference increments a hidden counter, and each removed reference decrements it; when the count reaches zero, Swift destroys the instance. At that moment, Swift automatically calls a special method called deinit, the counterpart to init, allowing developers to run cleanup logic before the object is removed from memory. Unlike structs, which hold independent copies of data and need no reference tracking, classes can be referenced by multiple variables simultaneously, making ARC essential. Developers can define deinit in their class but cannot call it manually — Swift triggers it exclusively when the last reference to an instance disappears.