mirror.swift

struct PostCode {
    var code: Int
}

struct Address {
    var street: String
    var post: PostCode
}

struct Man {
    var name: String = "John"
    var age: Int = 50
    var dutch: Bool = false
    var address: Address? = Address(street: "Market St.", post: PostCode(code: 111))
}

let john = Man()

extension Mirror {
    var properties: [(String, Child)] {
        return self.children.reduce([(String, Child)]()) {
            guard let propertyName = $1.label else { return $0 }
            return $0 + [(propertyName, $1)]
        }
    }
}


protocol JSON {
    func toJSON() throws -> AnyObject?
}

enum CouldNotSerializeError {
    case NoImplementation(source: Any, type: Mirror)
}

extension CouldNotSerializeError: ErrorType { }

extension JSON {
    func toJSON() throws -> AnyObject? {
        let mirror = Mirror(reflecting: self)
        if !mirror.properties.isEmpty {
            var result = [String:AnyObject]()
            for (key, child) in mirror.properties {
                guard let value = child.value as? JSON else {
                    throw CouldNotSerializeError.NoImplementation(source: self, type: mirror)
                }
                result[key] = try value.toJSON()
            }
            return result
        }
        return self as? AnyObject
    }
}

extension Man: JSON { }
extension String: JSON { }
extension Int: JSON { }
extension Bool: JSON { }
extension Address: JSON { }
extension PostCode: JSON { }
extension Optional: JSON {
    func toJSON() throws -> AnyObject? {
        guard let x = self else { return nil }
        if let value = x as? JSON {
            return try value.toJSON()
        }
        throw CouldNotSerializeError.NoImplementation(source: x, type: Mirror(reflecting: x))
    }
}

do {
    if let johnDescrip = try john.toJSON() {
        print(johnDescrip)
    }
} catch {
    print(error)
}