模拟Swift中的NSCache泛型方法

class Cache<Key: AnyObject, Value: AnyObject> {
    private let cache = NSCache<WrappedKey, Entry>()
    private let queue = DispatchQueue(label: "com.example.cacheQueue", attributes: .concurrent)

    func setObject(_ object: Value, forKey key: Key) {
        queue.async(flags: .barrier) {
            let entry = Entry(object: object)
            self.cache.setObject(entry, forKey: WrappedKey(key))
        }
    }

    func object(forKey key: Key) -> Value? {
        return queue.sync {
            let entry = self.cache.object(forKey: WrappedKey(key))
            return entry?.object
        }
    }

    private class WrappedKey: NSObject {
        let key: Key

        init(_ key: Key) {
            self.key = key
        }

        override var hash: Int {
            return key.hash
        }

        override func isEqual(_ object: Any?) -> Bool {
            if let otherKey = object as? WrappedKey {
                return key === otherKey.key
            } else {
                return false
            }
        }
    }

    private class Entry {
        let object: Value

        init(object: Value) {
            self.object = object
        }
    }
}