Mobx 状态树观察未按预期工作

如何解决Mobx 状态树观察未按预期工作

const Player = types.model({
    game_object: types.frozen()
});

const Zone = types.model({
    players: types.map(Player)
})
.actions(self => ({
    addplayer(params) {
        const playerGameObject = new PlayerGameObject(params);
        const newPlayer = Player.create({ game_object: playerGameObject })
        self.players.set(params.socket_id,newPlayer)
    }
}))

后来我有

observe(store.zone,"players",change => {
  console.log("Store zone players changed!!",change)
})

我不确定为什么这不起作用。我用字符串字段而不是 Player 尝试了类似的方法，它确实有效！

这是代码沙箱！

https://codesandbox.io/s/frosty-wave-wiy74?file=/src/index.js