added @asString attribute (needed for 2 fields in GCMNotification)

source/gcm.d

@@ -101,12 +101,14 @@ struct GCMNotification
 	string body_loc_key;
 
 	/// Indicates the string value to replace format specifiers in body string for localization.
+	@asString
 	string[] body_loc_args;
 
 	/// Indicates the key to the title string for localization.
 	string title_loc_key;
 
 	/// Indicates the string value to replace format specifiers in title string for localization.
+	@asString
 	string[] title_loc_args;
 }
 
@@ -205,6 +207,9 @@ class GCM
 	}
 }
 
+///
+enum asString;
+
 private:
 
 alias Alias(alias a) = a;
@@ -234,7 +239,6 @@ template isISOExtStringSerializable(T)
 }
 
 //TODO: support classes
-//TODO: `asString` fields
 JSONValue convert(T)(T value)
 {
 	import std.traits : isSomeFunction, isTypeTuple;
@@ -259,17 +263,28 @@ JSONValue convert(T)(T value)
 					continue;
 			}
 
+			JSONValue json = void;
+
 			static if (__traits(compiles, { auto v = JSONValue(__traits(getMember, value, field_name)); })) {
-				ret[stripName!field_name] = JSONValue(__traits(getMember, value, field_name));
+				json = JSONValue(__traits(getMember, value, field_name));
 			}
 			else static if (isISOExtStringSerializable!FieldN) {
-				ret[stripName!field_name] = __traits(getMember, value, field_name).toISOExtString();
+				json = __traits(getMember, value, field_name).toISOExtString();
 			}
 			else static if (is(FieldN == struct)) {
-				ret[stripName!field_name] = convert(__traits(getMember, value, field_name));
+				json = convert(__traits(getMember, value, field_name));
 			}
 			else
 				static assert(false, FieldN.stringof ~ " not supported");
+
+			//TODO: use hasUDA from 2.068
+			static if (__traits(getAttributes, __traits(getMember, value, field_name)).length > 0
+				&& __traits(isSame, __traits(getAttributes, __traits(getMember, value, field_name))[0], asString))
+			{
+				json = JSONValue(json.toString());
+			}
+
+			ret[stripName!field_name] = json;
 		}
 	}