lua - Using two same name function from different lua lib

Question

I have two different lib written by lua, but with same function name.

How can I choose one of them without modify the lib source?

require ('A') --A lib
require ('B') --B lib
test() -- function from B

If I want test function from A, how can I do?

Here is some way I tried.

LuaJ loading two functions with the same name from two different LuaScripts

I found this, but I don't want modify the lib source code.
Save the function as different name, like this:
```
require ('A') --A lib
_G.testA = test
require ('B') --B lib
_G.testB = test

testA() -- function from A
testB() -- function from B
```
But if someday a new function name testA() or testB() it break again.

And I still need to change all exist test() to testA() or testB().

Is there any better way?

Ideally the libraries you're using don't pollute the global namespace, but if they do, you could write something that does a diff of the environment and moves the library's global state into a scope. — Mud, Aug 24 '15 at 21:30

score 3 · Answer 1 · answered Aug 25 '15 at 01:16

This is exactly the reason why Lua modules shouldn't set global variables, but instead export all its functions/variables in a table that gets returned via require.

However, if your two modules are Lua modules, you can set a custom environment for each so that the global variables that the modules define end up in separate tables:

#!/usr/bin/lua

-- fallback implementation of package.searchpath for Lua 5.1
local searchpath = package.searchpath
-- not necessary if you have Lua 5.2+:
if not searchpath then
  local delim = package.config:match( "^(.-)\n" ):gsub( "%%", "%%%%" )

  function searchpath( name, path )
    local pname = name:gsub( "%.", delim ):gsub( "%%", "%%%%" )
    local msg = {}
    for subpath in path:gmatch( "[^;]+" ) do
      local fpath = subpath:gsub( "%?", pname )
      local f = io.open( fpath, "r" )
      if f then
        f:close()
        return fpath
      end
      msg[ #msg+1 ] = "\n\tnofile '"..fpath.."'"
    end
    return nil, table.concat( msg )
  end
end


-- table for storing the environments for each module
local environments = {}


-- clone of the standard Lua searcher which sets a custom environment
-- for the loaded chunk and stores it in the environments table.
local function my_lua_searcher( modname )
  local fpath, msg = searchpath( modname, package.path )
  if not fpath then
    return msg
  end
  local env = setmetatable( {}, { __index = _G } )
  env._G = env
  environments[ modname ] = env
  local f = assert( loadfile( fpath, nil, env ) )
  if setfenv then -- for Lua 5.1
    setfenv( f, env )
  end
  return f, fpath
end


-- replace the Lua searcher (at index 2)
local searchers = package.searchers or package.loaders
-- if someone added to package.searchers, we have no way of knowing
-- which function is the Lua searcher we want to replace:
assert( #searchers == 4, "package.searchers has been modified" )
searchers[ 2 ] = my_lua_searcher


-- test it:
require( "A" )
require( "B" )
environments[ "A" ].test()
environments[ "B" ].test()

iridian · Answer 2 · 2015-08-27T00:26:34.320

The code you have described

require ('A') --A lib
_G.testA = test
require ('B') --B lib
_G.testB = test

testA() -- function from A
testB() -- function from B

Is definitely one way to resolve your issue.

To avoid future issues you could put new functions inside a map

-- Example library.lua

-- Old code not in map
function my_old_func(params)
    -- do some stuff
end

-- New code goes down here
local mylibrary = {}
function mylibrary:my_awesome_func(params)
    my_old_func(params)
end

lua - Using two same name function from different lua lib

Here is some way I tried.

2 Answers2