Lua 中 Player State 中的变量没有按预期更新

在以下代码中，self.player.x 的值在初始化时被分配给 self.x，并在状态进入时稍微向左或向右调整。然后，PlayerPilotState 每帧操作 self.player.x，我的期望是 self.x 也会随之更新。像被分配给player的def.tilemap这样的项目在地图更改时确实会更新。但是，如何确保诸如self.x这样的变量也会更新自身呢？我知道我可以在每帧下更新该变量，但它似乎不够简洁，而且由于我对编程相对较新，我不明白为什么player.tilemap会更新，而此变量却不会。谢谢!

function PlayerPilotState:init(pilot, passenger)
    self.player = pilot
    self.passenger = passenger
    self.animation = Animation {
        frames = {2, 3, 2, 8},
        interval = 0.1
    }
    self.player.currentAnimation = self.animation

    -- x value at middle of players to make collisions more readable
    -- and scalable (for left/right pilot/passenger cases)
    self.x = self.player.x
end

function PlayerPilotState:enter(params)
    -- determine which side passenger is riding on
    self.ridingSide = params.ridingSide
    if self.ridingSide == 'left' then
        self.x = self.player.x - 1/2 * self.player.width
    else
        self.x = self.player.x + 1/2 * self.player.width
    end
end