KVC with Generics

kvc.swift

protocol KeyValueCodable {
    func value<T>(key: String) -> T?
    func valueForKey(key: String) -> Any?
}

extension KeyValueCodable {
    func value<T>(key: String) -> T? {
        guard let value = valueForKey(key) else { return nil }
        return value as? T
    }
    
    func valueForKey(key : String) -> Any? {
        
        let mirror = reflect(self)
        
        for index in 0 ..< mirror.count {
            let (childKey, childMirror) = mirror[index]
            if childKey == key {
                return childMirror.value
            }
        }
        return nil
    }
}

struct Person {
    var firstName: String
    var lastName: String
}

extension Person : KeyValueCodable {}

var p = Person(firstName: "David", lastName: "Owens")
p.valueForKey("firstName")
p.valueForKey("middleName")

let s: String? = p.value("firstName")
let i: Int? = p.value("firstName")