参考作为swift字典的关键 [英] Reference as key in swift dictionary

问题描述

字典键需要 Hashable 一致性：

class Test {}
var dictionary = [Test: String]() // Type 'Test' dies not conform to protocol 'Hashable'

class Test: NSObject {}
var dictionary = [Test: String]() // Works

如何获取纯Swift类实例的地址， hashValue ？

How to get address of pure Swift class instance to use as hashValue?

推荐答案

对于Swift 3（Xcode 8 beta 6或更高版本），使用 ObjectIdentifier 。

For Swift 3 (Xcode 8 beta 6 or later), use ObjectIdentifier.

class Test : Hashable {
    // Swift 2:
    var hashValue: Int { return unsafeAddressOf(self).hashValue }
    // Swift 3:
    var hashValue: Int { return ObjectIdentifier(self).hashValue }
}

func ==(lhs: Test, rhs: Test) -> Bool {
    return lhs === rhs
}

然后 a == b iff a 和 b 指的是同一个实例在这种情况下，课程（
和 a.hashValue == b.hashValue ）。

Then a == b iff a and b refer to the same instance of the class ( and a.hashValue == b.hashValue is satisfied in that case).

示例：

var dictionary = [Test: String]()
let a = Test()
let b = Test()
dictionary[a] = "A"
print(dictionary[a]) // Optional("A")
print(dictionary[b]) // nil

---

对于Swift 2.3及更早版本，您可以使用

---

For Swift 2.3 and earlier, you could use

/// Return an UnsafePointer to the storage used for `object`.  There's
/// not much you can do with this other than use it to identify the
/// object
func unsafeAddressOf(object: AnyObject) -> UnsafePointer<Void>

实现哈希值，身份运算符 ===
实现 Equable 协议。

to implement a hash value, and the identity operator === to implement the Equatable protocol.

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