一，基础
1，在lua中，table只是传递引用（即两个变量都指向同一片内存空间），所以不能用简单的 "=" 来copy两个表，并试图修改一个表中的值。
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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，原来的a也变了"
)
tb.b = 44
p(
"修改了原始的b = 44，引用的b也变了"
)
print(
"----------------------非表test"
)
a = 1
c = a
c = 3
print(
"a = "
.. a)
print(
"c = "
.. c)
打印结果：
--------------------------原始
tb.a = 11 tb.b = 22
tb_ref.a = 11 tb_ref.b22
--------------------------修改了引用的a = 33，原来的a也变了
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也变了
tb.a = 33 tb.b = 44
tb_ref.a = 33 tb_ref.b44
----------------------非表test
a = 1
c = 3
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结果：
当改变表的一个值以后，它的引用的值也发生了变化；
对于非表的一般常数来说，它的赋值不存在引用的问题；
2，table存储
1）table里保存数据，数据可以是任何类型，包括function。
2）table里也可以保存table
3）key代表数据存储的位置
4）value就是用特定的key存储的数据
二，记录遇见的一个关于table的问题
代码如下：
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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"
)
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nginx日志中的结果：
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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"
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结果分析：
1，lua中table相关操作包括做为function的参数都是引用操作，在function中对table node的key，value的相关操作都是对原table t的操作；
2，node = node["TOKEN"] 这一步操作相当于把node的内存地址指向了node["TOKEN"]的内存地址（即t["GET"]["TOKEN"]的内存地址），故之后对node的操作，都会影响到t["GET"]["TOKEN"]。
本文转自 leejia1989 51CTO博客，原文链接：http://blog.51cto.com/leejia/1945378，如需转载请自行联系原作者
