Instance & Lifetime
Core Idea
An Instance is a concrete value created from a Type.
Type
↓
Instance
Example:
struct Person {
let name: String
}
let person = Person(name: "Tom")
Person → Type
person → Instance
Lifecycle
Conceptually:
creation
↓
initialization
↓
use
↓
lifetime
↓
destruction / release
Initializer
An initializer establishes a valid initial state for an instance.
Person(name: "Tom")
Class Lifetime
For class instances, lifetime is related to reference ownership and ARC.
references
↓
instance lifetime
↓
deallocation
Important
Instance ≠ Type
Instance ≠ Memory Address
Instance ≠ "everything stored in memory"
An instance may contain stored state, while behavior and type information belong to other implementation layers.
