struct Position {
    var x: Int
    var y: Int
    
}

extension Position: Equatable, Hashable {
    
}

let availablePositions = [Position(x: 0, y: 0), Position(x: 0, y: 1), Position(x: 1, y: 0)]
let gemPosition = Position(x: 1, y: 0)

for position in availablePositions {
    if gemPosition == position {
        print("Gem found at (\(position.x), \(position.y))!")
    } else {
        print("No gem at (\(position.x), \(position.y))")
    }
}

if availablePositions.contains(gemPosition) {
    print("availablePositions 包含 gemPosition")
} else {
    print("availablePositions 不包含 gemPosition")
}

class Player {
    var name: String
    var position: Position
    
    init(name: String, position: Position) {
        self.name = name
        self.position = position
    }
}

// 注意点： == 和 hash(into:) 方法中必须使用相同的属性（名称和数量都要相同）
extension Player: Equatable {
    static func ==(lhs: Player, rhs: Player) -> Bool {
        return lhs.name == rhs.name && lhs.position == rhs.position
    }
}

extension Player: Hashable {
    func hash(into hasher: inout Hasher) {
        hasher.combine(name)
        hasher.combine(position)
    }
}

let p0 = Player(name: "0", position: Position(x: 0, y: 0))
let p1 = Player(name: "1", position: Position(x: 1, y: 1))
let p2 = Player(name: "0", position: Position(x: 0, y: 0))
let ps = [p0, p1, p2]

if p0 == p2 {
    print("p0 = p2")
}

if p0 != p1 {
    print("p0 != p1")
}

if ps.contains(p1) {
    print("ps 包含 p1")
}

class MyNSObjectSubclass: NSObject {
    var name: String
    var position: Position
    
    init(name: String, position: Position) {
        self.name = name
        self.position = position
    }
}
// 注意点： isEqual 和 hash 方法中必须使用相同的属性（名称和数量都要相同）
extension MyNSObjectSubclass {
    override func isEqual(_ object: Any?) -> Bool {
        guard let other = object as? MyNSObjectSubclass
            else { return false }
        return self.name == other.name
            && self.position == other.position
    }
    override var hash: Int {
        var hasher = Hasher()
        hasher.combine(name)
        hasher.combine(position)
        return hasher.finalize()
    }
}

let obj0 = MyNSObjectSubclass(name: "0", position: Position(x: 0, y: 0))
let obj1 = MyNSObjectSubclass(name: "1", position: Position(x: 1, y: 1))
let obj2 = MyNSObjectSubclass(name: "0", position: Position(x: 0, y: 0))
let objs = [obj0, obj1, obj2]

if obj0 == obj2 {
    print("obj0 = obj2")
}

if obj0 != obj1 {
    print("obj0 != obj1")
}

if objs.contains(obj1) {
    print("objs 包含 obj1")
}