How to make Json.stringify ignore certain class memebers? - json

Question

I'm using the latest Haxe and HaxeFlixel to make a simple game prototype.
I have the following class...
class GameData
{
public var playerHealth: Int;
public var playerScore: Int;
public var levelName: String;
public function new(playerHealth: Int = 0, playerScore: Int = 0, levelName: String = "")
{
this.playerHealth = playerHealth;
this.playerScore = playerScore;
this.levelName = levelName;
}
}
I convert it to JSON as follows...
Json.stringify(new GameData(64, 512, "Level 1"));
Is there's a way I can make it so the stringify ignores certain members?

Answer 1

haxe.Json has no mechanism to exclude fields, so I would recommend using a third-party library such as json2object that does. Here you can simply annotate fields that should be ignored with #:jignored:
#:jignored
public var levelName:String;
var data = new GameData(100, 10, "Level 1");
var json = new json2object.JsonWriter<GameData>().write(data);
trace(json); // {"playerHealth": 100,"playerScore": 10}
There are some possible workarounds that don't involve adding a library to your project, but they don't seem very nice:
Don't serialize the object directly, but a structure that only includes the desired fields:
var data = new GameData(100, 10, "Level 1");
var json = Json.stringify({
playerHealth: data.playerHealth,
playerScore: data.playerScore
});
trace(json); // {"playerHealth":100,"playerScore":10}
Remove the unwanted fields after serialization - this seems rather hacky as it involves a lot of unnecessary overhead due to an additional Json.parse() and Json.stringify() call:
var json = Json.stringify(new GameData(100, 10, "Level 1"));
var data:haxe.DynamicAccess<String> = Json.parse(json);
data.remove("levelName");
json = Json.stringify(data);
trace(json); // {"playerHealth":100,"playerScore":10}

Answer 2

Depending on your exact situation, it can be desirable to make a slightly modified version of standard library's JsonPrinter - for example, in GMEdit I allow JSON objects to have an hxOrder: Array<String> field, which, if provided, determines the field order for printing, and is initialized to a static array. You can make a similar scheme for field inclusion/exclusion.