Make Dictionary conform to value type protocol - swift

Question

This is simplified code that doesn't compile. Is there anyway to make this work in Swift? Thanks.
protocol Person {
var name:String { get }
var age:Int { get }
}
extension Dictionary : Person {
var name: String {
return self["name"] as String
}
var age: Int {
return self["Int"] as Int
}
}
Let me give some context to why I would want to do this.
Lets say I have some person data coming in over the wire as json. As I pass it through JSONSerialization I get a [String:AnyObject] Dictionary back.
So I would like to declare the JSON data interfaces in protocols, make the dictionary objects conform to the protocols and then extract the values from the dictionaries via typed properties, rather then via magic strings and casts. This way the client code would only know about protocol types even though they are implemented as dictionaries behind the curtain.
Not sure it's doable or a good idea, just wanted to try it. But compiler is giving me all sorts of trouble.

Answer 1

I understand you want to encapsulate the logic to link a json to it's model representation.
The suggested solution
First of all I am suggesting another way to achieve what you are looking for instead
Look at this Struct.
struct Person {
let name: String
let age: Int
init?(json: [String:Any]) {
guard let name = json["name"] as? String, age = json["age"] as? Int else { return nil }
self.name = name
self.age = age
}
}
The logic to extract data from the json is encapsulated into its initializer. And if the provided json is not valid the initialization fails. It's safe because it will never crash and it's easy to use.
The direct answer (don't do this at home!)
protocol Person {
var name: String? { get }
var age: Int? { get }
}
extension Dictionary : Person {
private var dictWithStringKeys: [String:Any] {
return reduce([String:Any]()) { (dict, elm) -> [String:Any] in
var dict = dict
if let key = elm.0 as? String {
dict[key] = elm.1
}
return dict
}
}
var name: String? {
return dictWithStringKeys["name"] as? String
}
var age: Int? {
return dictWithStringKeys["age"] as? Int
}
}