lua中表table的拷贝而不是引用的操作方法

lua中的table类型相互赋值都是相互引用，也就是修改被赋值或者赋值的table都会影响双方的内容，相当于两个指针的指向是一样的，修改其中一个指针的指向内容，另一个所指向的内容也相应的变化，想通过赋值得到一个copy的想法看来有点天真了。

其实这个特性是官方刻意为之的，官方也给出了足够的理由和解决方法，偶然之前搜索的时候找到了他们的解决方法，如下所述，如果不想看内容，那哥们就告诉你结论得了，那就是直接拷贝deepcopy这个函数用就行了！！！！！

原文链接：http://lua-users.org/wiki/CopyTable

The Lua standard libraries do not provide a function to copy a table. However, it is relatively simple to implement such a function.

A generic table.copy function is not guaranteed to suit all use-cases, as there are many different aspects which must be selected for the specific situation. For example: should metatables be shared or copied? Should we check userdata for a __copy metamethod? These questions (as well as many others) must be asked and answered by the developer.

Some of the Lua "extended standard libraries", such as Penlight and stdlib provide ready-made copy functions for convenience. Check if they suit your use-case before implementing your own.

The following functions provide a base to work off of:

Quick & Dirty

function table.clone(org)  return {table.unpack(org)}endlocal abc = {5,12,1}local def = table.clone(abc)table.sort(def)print(abc[2], def[2]) -- 125

Shallow Copy

This a simple, naive implementation. It only copies the top level value and its direct children; there is no handling of deeper children, metatables or special types such as userdata or coroutines. It is also susceptible to influence by the __pairs metamethod.

function shallowcopy(orig)    local orig_type = type(orig)    local copy    if orig_type == '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 copyend

Deep Copy

A deep copy copies all levels (or a specific subset of levels).

Here is a simple recursive implementation that additionally handles metatables and avoid the __pairs metamethod.

function deepcopy(orig)    local orig_type = type(orig)    local copy    if orig_type == 'table' then        copy = {}        for orig_key, orig_value in next, orig, nil do            copy[deepcopy(orig_key)] = deepcopy(orig_value)        end        setmetatable(copy, deepcopy(getmetatable(orig)))    else -- number, string, boolean, etc        copy = orig    end    return copyend

Additionally, it is recursive which means it may overflow the stack for large tables.

Non-recursive Deep Copy

A more flexible (non-recursive) deepcopy implementation is available from [this GitHub gist]. It allows for varying rules on how to copy special types, metatables, and function upvalues (including joining). Please see the comments for usage.