无法使用元表从lua中的基类创建实例

-- 定义基类
local BaseClass = {
  name = "BaseClass",
}

function BaseClass:new()
  local instance = {}
  setmetatable(instance, self)
  self.__index = self
  return instance
end

function BaseClass:sayHello()
  print("Hello from BaseClass")
end

-- 定义派生类
local DerivedClass = {
  name = "DerivedClass",
}

setmetatable(DerivedClass, { __index = BaseClass })

function DerivedClass:new()
  local instance = BaseClass:new()
  setmetatable(instance, self)
  self.__index = self
  return instance
end

function DerivedClass:sayHello()
  print("Hello from DerivedClass")
end

-- 创建实例
local baseInstance = BaseClass:new()
baseInstance:sayHello()  -- 输出: Hello from BaseClass

local derivedInstance = DerivedClass:new()
derivedInstance:sayHello()  -- 输出: Hello from DerivedClass