ObjectIdentifier protocol : object identity 비교하기

31 May 2019 | ObjectIdentifier • identity

ObjectIdentifier

A unique identifier for a class instance or metatype.

객체의 Identity 가 같은지/다른지 판단해주는 struct

struct ObjectIdentifier

사용되는 곳

Example. Equatable protocol

protocol Equatable {
  @inlinable // trivial-implementation
  public func === (lhs: AnyObject?, rhs: AnyObject?) -> Bool {
    switch (lhs, rhs) {
    case let (l?, r?):
      return ObjectIdentifier(l) == ObjectIdentifier(r)
    case (nil, nil):
      return true
    default:
      return false
    }
  }
}

Swift 에서는 class instance 와 meta type 만 unique identity를 가진다
struct, enum, function, tuple 에는 identity 란 개념이 없다
eqaulity vs. Identity

Identity Operator
```
func === (lhs: AnyObject?, rhs: AnyObject?) -> Bool
```
Returns a Boolean value indicating whether two references point to the same object instance.

reference 가 같은 instance 를 가리키는지 판단

Reference