无法将NSObject子类用作Swift字典中的键

Question

我上了这个课：

class NSObjectObject: NSObject {
    let important: String
    let notImportant: String

    init(important: String, notImportant: String) {
        self.important = important
        self.notImportant = notImportant
    }

    static func == (lhs: NSObjectObject, rhs: NSObjectObject) -> Bool {
        return lhs.hashValue == rhs.hashValue
    }

    override var hash: Int {
        return important.hashValue
    }
}

我有这个测试：

class HashTests: XCTestCase {

    func testNSObjectObject() {
        var dict = [NSObjectObject: String]()

        let obj1 = NSObjectObject(important: "A", notImportant: "B")
        let obj2 = NSObjectObject(important: "C", notImportant: "D")

        dict[obj1] = "obj1"
        dict[obj2] = "obj2"

        let obj1Copy = NSObjectObject(important: "A", notImportant: "B")

        print("obj1 => \(obj1.hashValue)")
        print("obj2 => \(obj2.hashValue)")
        print("obj1Copy => \(obj1Copy.hashValue)")

        XCTAssertEqual(dict[obj1Copy], "obj1")
    }
}

哪个失败

  

XCTAssertEqual失败：（“ nil”）不等于（“” Optional（“ obj1”）“）

此外，打印语句的输出为：

obj1 => -406393155368168228
obj2 => -3721711324458125961
obj1Copy => -406393155368168228