fix(identifiable): use a string id instead of the object id

includes conversion methods

Author: jaredcnance

src/JsonApiDotNetCore/Internal/TypeHelper.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Reflection;
+
+namespace JsonApiDotNetCore.Internal
+{
+    public static class TypeHelper
+    {
+        public static object ConvertType(object value, Type type)
+        {
+            if(value == null)
+                return null;
+
+            if (type.GetTypeInfo().IsGenericType && type.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
+                type = Nullable.GetUnderlyingType(type);            
+
+            var stringValue = value.ToString();
+            
+            if(type == typeof(Guid))
+                return Guid.Parse(stringValue);
+
+            return Convert.ChangeType(stringValue, type);
+        }
+    }
+}

src/JsonApiDotNetCore/Models/IIdentifiable.cs

@@ -2,7 +2,7 @@ namespace JsonApiDotNetCore.Models
 {
     public interface IIdentifiable
     {
-        object Id { get; set; }
+        string Id { get; set; }
     }
 
     public interface IIdentifiable<T> : IIdentifiable

src/JsonApiDotNetCore/Models/Identifiable.cs

@@ -1,3 +1,7 @@
+using System;
+using System.Reflection;
+using JsonApiDotNetCore.Internal;
+
 namespace JsonApiDotNetCore.Models
 {
     public class Identifiable : Identifiable<int>
@@ -7,10 +11,31 @@ public class Identifiable<T> : IIdentifiable<T>, IIdentifiable
     {
         public virtual T Id { get; set; }
 
-        object IIdentifiable.Id
+        string IIdentifiable.Id
+        {
+            get { return GetStringId(Id); }
+            set { Id = (T)GetConcreteId(value); }
+        }
+
+        protected virtual string GetStringId(object value)
+        {
+            var type = typeof(T);
+            var stringValue = value.ToString();
+
+            if(type == typeof(Guid))
+            {
+                var guid = Guid.Parse(stringValue);
+                return (guid == Guid.Empty ? string.Empty : stringValue);
+            }
+
+            if(stringValue == "0") return string.Empty;
+
+            return stringValue;
+        }
+
+        protected virtual object GetConcreteId(string value)
         {
-            get { return Id; }
-            set { Id = (T)value; }
+            return TypeHelper.ConvertType(value, typeof(T));
         }
     }
 }

src/JsonApiDotNetCore/Serialization/JsonApiDeSerializer.cs

@@ -60,7 +60,7 @@ private static object DataToObject(DocumentData data, IJsonApiContext context)
             var identifiableEntity = (IIdentifiable)entity;
 
             if (data.Id != null)
-                identifiableEntity.Id = ChangeType(data.Id, identifiableEntity.Id.GetType());
+                identifiableEntity.Id = data.Id;
 
             return identifiableEntity;
         }
@@ -80,7 +80,7 @@ private static object _setEntityAttributes(
                 object newValue;
                 if (attributeValues.TryGetValue(attr.PublicAttributeName.Dasherize(), out newValue))
                 {
-                    var convertedValue = ChangeType(newValue, entityProperty.PropertyType);
+                    var convertedValue = TypeHelper.ConvertType(newValue, entityProperty.PropertyType);
                     entityProperty.SetValue(entity, convertedValue);
                 }
             }
@@ -112,27 +112,15 @@ private static object _setRelationships(
                     if (data == null) continue;
 
                     var newValue = data["id"];
-                    var convertedValue = ChangeType(newValue, entityProperty.PropertyType);
+                    var convertedValue = TypeHelper.ConvertType(newValue, entityProperty.PropertyType);
                     entityProperty.SetValue(entity, convertedValue);
                 }
             }
 
             return entity;
         }
 
-        private static object ChangeType(object value, Type conversion)
-        {
-            var t = conversion;
-
-            if (t.GetTypeInfo().IsGenericType && t.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
-            {
-                if (value == null)
-                    return null;
 
-                t = Nullable.GetUnderlyingType(t);
-            }
-
-            return Convert.ChangeType(value, t);
-        }
+        
     }
 }