一,基礎
1,在lua中,table隻是傳遞引用(即兩個變量都指向同一片記憶體空間),是以不能用簡單的 "=" 來copy兩個表,并試圖修改一個表中的值。
tb = {}
tb.a = 11
tb.b = 22
tb_ref = tb
function p(tip)
print("--------------------------" .. tip)
print("tb.a = " .. tb.a .. " " .. "tb.b = " .. tb.b)
print("tb_ref.a = " .. tb_ref.a .. " " .. "tb_ref.b" .. tb_ref.b)
end
p("原始")
tb_ref.a = 33
p("修改了引用的a = 33,原來的a也變了")
tb.b = 44
p("修改了原始的b = 44,引用的b也變了")
print("----------------------非表test")
a = 1
c = a
c = 3
print("a = " .. a)
print("c = " .. c)
列印結果:
--------------------------原始
tb.a = 11 tb.b = 22
tb_ref.a = 11 tb_ref.b22
--------------------------修改了引用的a = 33,原來的a也變了
tb.a = 33 tb.b = 22
tb_ref.a = 33 tb_ref.b22
--------------------------修改了原始的b = 44,引用的b也變了
tb.a = 33 tb.b = 44
tb_ref.a = 33 tb_ref.b44
----------------------非表test
a = 1
c = 3
結果:
當改變表的一個值以後,它的引用的值也發生了變化;
對于非表的一般常數來說,它的指派不存在引用的問題;
2,table存儲
1)table裡儲存資料,資料可以是任何類型,包括function。
2)table裡也可以儲存table
3)key代表資料存儲的位置
4)value就是用特定的key存儲的資料
二,記錄遇見的一個關于table的問題
代碼如下:
local cjson = require("cjson")
local t = {["GET"] = {["/a"] = "f"}}
function hehe(node)
node["TOKEN"] = node["TOKEN"] or {}
ngx.log(ngx.ERR, "0", cjson.encode(t["GET"]))
ngx.log(ngx.ERR, "0", cjson.encode(node))
ngx.log(ngx.ERR, "0", tostring(node))
node = node["TOKEN"]
ngx.log(ngx.ERR, "1", cjson.encode(t["GET"]))
ngx.log(ngx.ERR, "1", cjson.encode(node))
ngx.log(ngx.ERR, "1", tostring(node))
node["TOKEN"] = "123"
ngx.log(ngx.ERR, "2", cjson.encode(t["GET"]))
ngx.log(ngx.ERR, "2", cjson.encode(node))
ngx.log(ngx.ERR, "2", tostring(node))
end
hehe(t["GET"])
ngx.say("ok")
nginx日志中的結果:
2017/07/10 15:28:16 [error] 20400#0: *749 [lua] access_by_lua(nginx.conf:138):8: hehe(): 0{"\/a":"f","TOKEN":{}}, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:8888"
2017/07/10 15:28:16 [error] 20400#0: *749 [lua] access_by_lua(nginx.conf:138):9: hehe(): 0{"\/a":"f","TOKEN":{}}, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:8888"
2017/07/10 15:28:16 [error] 20400#0: *749 [lua] access_by_lua(nginx.conf:138):10: hehe(): 0table: 0x41dfca60, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:8888"
2017/07/10 15:28:16 [error] 20400#0: *749 [lua] access_by_lua(nginx.conf:138):13: hehe(): 1{"\/a":"f","TOKEN":{}}, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:8888"
2017/07/10 15:28:16 [error] 20400#0: *749 [lua] access_by_lua(nginx.conf:138):14: hehe(): 1{}, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:8888"
2017/07/10 15:28:16 [error] 20400#0: *749 [lua] access_by_lua(nginx.conf:138):15: hehe(): 1table: 0x41e011e0, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:8888"
2017/07/10 15:28:16 [error] 20400#0: *749 [lua] access_by_lua(nginx.conf:138):18: hehe(): 2{"\/a":"f","TOKEN":{"TOKEN":"123"}}, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:8888"
2017/07/10 15:28:16 [error] 20400#0: *749 [lua] access_by_lua(nginx.conf:138):19: hehe(): 2{"TOKEN":"123"}, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:8888"
2017/07/10 15:28:16 [error] 20400#0: *749 [lua] access_by_lua(nginx.conf:138):20: hehe(): 2table: 0x41e011e0, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "127.0.0.1:8888"
結果分析:
1,lua中table相關操作包括做為function的參數都是引用操作,在function中對table node的key,value的相關操作都是對原table t的操作;