==と===に関する同値と同一の確認。UIViewはクラスなはずなのに、==が使えるのはなぜかと、===が何を同一としているのかを調べてみた。

Equatablity.swift

// 参考・関連
// https://qiita.com/omochimetaru/items/2aa00c7cb0eef4e57999
// https://qiita.com/omochimetaru/items/c95e0d36ae7f1b1a9052
// https://stackoverflow.com/questions/24938503/nsobject-is-hashable-but-a-protocol-that-adopts-nsobject-is-not
// https://developer.apple.com/documentation/swift/1538988

import Foundation

class Hoge {}

let hoge1 = Hoge()
let hoge2 = Hoge()
let hoge3 = hoge1

let hoge1Ref: Unmanaged<Hoge> = Unmanaged<Hoge>.passUnretained(hoge1)
let rawHoge1: UnsafeMutableRawPointer = hoge1Ref.toOpaque()

let hoge3Ref: Unmanaged<Hoge> = Unmanaged<Hoge>.passUnretained(hoge3)
let rawHoge3: UnsafeMutableRawPointer = hoge3Ref.toOpaque()

let hoge2Ref: Unmanaged<Hoge> = Unmanaged<Hoge>.passUnretained(hoge2)
let rawHoge2: UnsafeMutableRawPointer = hoge2Ref.toOpaque()

//hoge1 == hoge2
//hoge1 == hoge3
hoge1 === hoge2
hoge1 === hoge3

// hoge1.hash
// hoge2.hash
// hoge3.hash
// hoge1.hashValue
// hoge2.hashValue
// hoge3.hashValue



import UIKit

// UIViewはNSObjectを継承していて、NSObjectがEquatableにも準拠しているので==が使える

let v1 = UIView()
let v2 = UIView()
let v3 = v1

let v1Ref: Unmanaged<UIView> = Unmanaged<UIView>.passUnretained(v1)
let rawV1: UnsafeMutableRawPointer = v1Ref.toOpaque()

let v3Ref: Unmanaged<UIView> = Unmanaged<UIView>.passUnretained(v3)
let rawV3: UnsafeMutableRawPointer = v3Ref.toOpaque()

let v2Ref: Unmanaged<UIView> = Unmanaged<UIView>.passUnretained(v2)
let rawV2: UnsafeMutableRawPointer = v2Ref.toOpaque()

v1 == v2
v1 == v3
v1 === v2
v1 === v3

v1.hash
v2.hash
v3.hash

v1.hashValue
v2.hashValue
v3.hashValue