A generic wrapper for NSHashTable on Swift <= 2.3

HashTable.swift

import Foundation

#if swift(>=3.0)
typealias HashTable<ObjectType: AnyObject> = NSHashTable<ObjectType>
#else
struct HashTable<ObjectType: AnyObject> {
    
    private let _table = NSHashTable.weakObjectsHashTable()
    
    static func weakObjects() -> HashTable<ObjectType> {
        return HashTable<ObjectType>()
    }
    
    var count: Int {
        return _table.count
    }
    
    func member(object: ObjectType?) -> ObjectType? {
        return _table.member(object) as? ObjectType
    }
    
    func add(object: ObjectType?) {
        _table.addObject(object)
    }
    
    func remove(object: ObjectType?) {
        _table.removeObject(object)
    }
    
    func removeAllObjects() {
        _table.removeAllObjects()
    }
    
    var allObjects: [ObjectType] {
        return unsafeBitCast(_table.allObjects, [ObjectType].self)
    }
    
    var anyObject: ObjectType? {
        return _table.anyObject as? ObjectType
    }
    
    func contains(object: ObjectType?) -> Bool {
        return _table.containsObject(object)
    }
}

extension HashTable: SequenceType {
    
    func generate() -> NSFastGenerator {
        return _table.objectEnumerator().generate()
    }
}
    
extension HashTable: CustomStringConvertible {
    
    var description: String {
        var string = "\(self.dynamicType) {\n"
        _table.allObjects.enumerate().forEach { idx, obj in
            string += "[\(idx)] \(obj)\n"
        }
        string += "}"
        return string
    }
}
#endif