fix generate optional double

Author: knottx

lib/common/utils/json_serialize/sintaxe.dart

@@ -127,21 +127,24 @@ class TypeDefinition {
         fixFieldName(key, typeDef: this, privateField: privateField);
     if (isPrimitive) {
       if (name == 'List') {
-        return "$fieldKey = json['$key'].cast<$subtype>();";
+        return "$fieldKey = $jsonKey.cast<$subtype>();";
       }
-      return "$fieldKey = json['$key'];";
+      if (name == 'double?') {
+        return "$fieldKey = ($jsonKey as num?)?.toDouble();";
+      }
+      return "$fieldKey = $jsonKey;";
     } else if (name == 'List' && subtype == 'DateTime') {
-      return "$fieldKey = json['$key'].map((v) => DateTime.tryParse(v));";
+      return "$fieldKey = $jsonKey.map((v) => DateTime.tryParse(v));";
     } else if (name == 'DateTime') {
-      return "$fieldKey = DateTime.tryParse(json['$key']);";
+      return "$fieldKey = DateTime.tryParse($jsonKey);";
     } else if (name == 'List') {
       // list of class
-      return "if (json['$key'] != null) {\n\t\t\t$fieldKey = <$subtype>[];"
-          "\n\t\t\tjson['$key'].forEach((v) { "
+      return "if ($jsonKey != null) {\n\t\t\t$fieldKey = <$subtype>[];"
+          "\n\t\t\t$jsonKey.forEach((v) { "
           '$fieldKey${PubspecUtils.nullSafeSupport ? '?' : ''}.add($subtype.fromJson(v)); });\n\t\t}';
     } else {
       // class
-      return "$fieldKey = json['$key'] != null ?"
+      return "$fieldKey = $jsonKey != null ?"
           ' ${_buildParseClass(jsonKey)} : null;';
     }
   }