NSCoder Extension for Encode Swift String and Specific Struct

archiving.swift

extension NSCoder {
    //  Encode String
    func encodeString(string:String, forKey key:String) {
        self.encodeObject(string as NSString, forKey:key)
    }
    
    func decodeStringForKey(key:String) -> String {
        let ns =  self.decodeObjectForKey(key) as! NSString
        return ns as String
    }

    //  Encode Array of Primary Types
    func encodeArray<C:CollectionType, T where C.Generator.Element == T>(array:C, forKey key:String) -> NSData {
        let length = sizeof(T.Type) * array.count
        var ptr = UnsafeMutablePointer<T>.alloc(array.count)

        var arrptr = UnsafeMutableBufferPointer<T>(start:ptr, count:array.count)
        for (i, n) in enumerate(array) {
            arrptr[i] = n
        }

        let tempData = NSData(bytes:ptr, length:length)
        self.encodeObject(tempData, forKey:key)
        ptr.dealloc(array.count)
    }


    func decodeArrayForKey<T>(key:String) -> Array<T> {
        let data = self.decodeObjectForKey(key)
        let length = data.length
        let count = length / sizeof(T.Type)
        var ptr = UnsafeMutablePointer<T>.alloc(count)
        data.getBytes(ptr, length:length)
        var arrptr = UnsafeBufferPointer(start:ptr, count:count)
        let result = Array(arrptr)
        ptr.dealloc(count)
        return result
    }

    //  Encode Specific Struct Type
    /*
    struct Person {
        let firstName:String
        let lastName:String
        let age:Int
    }
    */
    
    func encodePerson(person:Person, forKey key:String) {
        self.encodeInteger(person.age, forKey:"\(key)_age")
        self.encodeString(person.lastName, forKey:"\(key)_lastName")
        self.encodeString(person.firstName, forKey:"\(key)_firstName")
    }
    
    func decodePersonForKey(key:String) -> Person {
        let fN = self.decodeStringForKey("\(key)_firstName")
        let lN = self.decodeStringForKey("\(key)_lastName")
        let age = self.decodeIntegerForKey("\(key)_age")
        return Person(firstName:fN, lastName:lN, age:age)
    }
}