将变量分配给另一个变量名。

如何将变量赋值给另一个变量名？例如，我想实现以下内容：

        function ballPosition(ballType)
            balls[ball].ballType.x  = balls[ball].x
            balls[ball].ballType.y  = balls[ball].y
        end

    if balls[ball].type == "fireBall" then
        ballPosition(fireBall)
    elseif balls[ball].type == "powerLessBall" then
        ballPosition(powerLessBall)
    end

当前我有：

        if balls[ball].type == "fireBall" then
            balls[ball].fireBall.x  = balls[ball].x
            balls[ball].fireBall.y  = balls[ball].y
        elseif balls[ball].type == "powerLessBall" then
            balls[ball].powerLessBall.x = balls[ball].x
            balls[ball].powerLessBall.y     = balls[ball].y
        end