今天在写游戏的时候，遇到了一个数据问题，就开始查资料
代码如下
代码语言：javascript复制--- Deep copies a table into a new table.
-- Tables used as keys are also deep copied, as are metatables
-- @param orig The table to copy
-- @return Returns a copy of the input table
local function deep_copy(orig)
local copy
if type(orig) == "table" then
copy = {}
for orig_key, orig_value in next, orig, nil do
copy[deep_copy(orig_key)] = deep_copy(orig_value)
end
setmetatable(copy, deep_copy(getmetatable(orig)))
else
copy = orig
end
return copy
end
--- Copies a table into a new table.
-- neither sub tables nor metatables will be copied.
-- @param orig The table to copy
-- @return Returns a copy of the input table
local function shallow_copy(orig)
local copy
if type(orig) == "table" then
copy = {}
for orig_key, orig_value in pairs(orig) do
copy[orig_key] = orig_value
end
else -- number, string, boolean, etc
copy = orig
end
return copy
end例子如下：
深拷贝
代码语言：javascript复制local a = { aa = 1, bb = 2, cc = { dd = { ee = 3 } } }
--local b = deep_copy(a)
local b = shallow_copy(a)
b.cc.dd.ee = 111
b.bb = 111
ngx.say(cjson.encode(a))
ngx.say(cjson.encode(b))结果：{“aa”:1,”bb”:2,”cc”:{“dd”:{“ee”:111}}}
{“aa”:1,”bb”:111,”cc”:{“dd”:{“ee”:111}}}
浅拷贝
代码语言：javascript复制local men = { mkey = 555 }
local a = { aa = 1, bb = 2, cc = { dd = { ee = { ff = 3 } } } }
setmetatable(a, { __index = men })
local b = deep_copy(a)
ngx.say(a.cc.dd.ee.ff)
ngx.say(a.mkey)
ngx.say(b.mkey)3
555
555
