lua元表学习

Posted 2021-01-29 blackteeth

 1 a = {1, 2}
 2 b= {3, 4}
 3 
 4 vector2 = {}
 5 function vector2.Add(v1, v2)
 6     if(v1 == nil or v2 == nil)then
 7         return nil
 8     end
 9     local res = {}
10     res[1] = v1[1] + v2[1]
11     res[2] = v2[1] + v2[2]
12     return res;
13 end
14 
15 vector2.__add = vector2.Add
16 
17 setmetatable(a, vector2)
18 setmetatable(b, vector2)
19 
20 res = a + b
21 
22 print(res[1], res[2])

元表操作的一般流程

1.定义原始表

2.定义元表

3.定义元方法

4.设置元表

 1 str1 = {"I", "love", "lua"}
 2 
 3 myStr = {}
 4 function myStr.ToString(str)
 5     res = {}
 6     for i = 1, #str do
 7         res[i] = str[i]
 8     end
 9     return table.concat(res, " ")
10 end
11 
12 myStr.__tostring = myStr.ToString
13 
14 setmetatable(str1, myStr)
15 
16 print(str1)

 

str2 = {str1 = "我",str2 = "爱", str3 = "撸啊"}
myStr = {}
function myStr.ToString(str)
    res = {}
    for  i,v in pairs(str) do
       res[#res+1] = v
    end

    return table.concat(res, " ")
end

myStr.__tostring = myStr.ToString

setmetatable(str2, myStr)

print(str2)