function create(name, id)
      local obj = { name = name, id = id }
      function obj:SetName(name)
        self.name = name
      end
      function obj:GetName()
        return self.name
      end
      function obj:SetId(id)
        self.id = id
      end
      function obj:GetId()
        return self.id
      end
      return obj
   end

   o1 = create("Sam", 001)

   print("o1's name:", o1:GetName(), "o1's id:", o1:GetId())

   o1:SetId(100)
   o1:SetName("Lucy")

   print("o1's name:", o1:GetName(), "o1's id:", o1:GetId())

o1's name: Sam o1's id: 1
o1's name: Lucy o1's id: 100

function obj:method(a1,a2,…)…end --等价于
    function obj.method(self,a1,a2,…)…end --等价于
    obj.method=function(self,a1,a2,...)...end

obj:method(a1,a2,...) --等价于
    obj.method(obj,a1,a2,...)