add unkeyedcontainer

MVMCore/MVMCore/Models/Model/Model.swift

@@ -10,7 +10,7 @@ import Foundation
 
 public protocol Model: Codable {
 
-    static var identifier: String { get set }
+    static var identifier: String { get }
     
 }
 

MVMCore/MVMCore/Models/Model/ModelRegistry.swift

@@ -24,6 +24,27 @@ public struct ModelRegistry {
     }
 }
 
+extension UnkeyedDecodingContainer {
+    
+    public mutating func decodeUnKeyedIfPresent<T, C:CodingKey>(_ type: T.Type, typeCodingKey: C) throws -> T? where T : Decodable {
+        let meta = try self.nestedContainer(keyedBy: C.self)
+        guard let type = try meta.decodeIfPresent(String.self, forKey: typeCodingKey) else {
+            return nil
+        }
+
+        //get the type
+        guard let found = ModelRegistry.types[type] else {
+            throw ModelRegistry.Error.decoderErrorModelNotMapped
+        }
+        let model = try self.decode(found)
+        
+        guard let m = model as? T else {
+            throw ModelRegistry.Error.decoderError
+        }
+        return m
+    }
+    
+}
 
 extension KeyedDecodingContainer where Key: CodingKey {
     
@@ -48,7 +69,7 @@ extension KeyedDecodingContainer where Key: CodingKey {
     public func decodeIfPresent<T, C:CodingKey>(codingKey: KeyedDecodingContainer<K>.Key, typeCodingKey: C) throws -> T? {
 
         //get the type string
-        let meta = try self.nestedContainer(keyedBy: type(of: typeCodingKey), forKey: codingKey)
+        let meta = try self.nestedContainer(keyedBy: C.self, forKey: codingKey)
         guard let type = try meta.decodeIfPresent(String.self, forKey: typeCodingKey) else {
             return nil
         }