Best practice for overriding a local function

DaanVanYperen

Working on the Skulks WIth Shotguns mod, going great so far. I'm new to lua and ns2 modding though so having some trouble with the basics.

What would you suggest to be the best method for overriding a local function?

Specifically AssignPlayerToEgg, in AlienTeam.lua.

My best solution is overriding AlienTeam:Update (which calls AssignPlayerToEgg) in a mod file, but that leads to a lot of local functions having to end up in my mod file as well. I figure I might be overlooking some basic method of achieving just a single local function override.

Thanks!

Soul_Rider

If you can specify what you are trying to achieve, we can possibly advise on a way to do it. Why would you not just edit the function, rather than override it?


If you could supply more info, I am sure we can help

Oh and good luck with the programming, Howser told me you had finally bitten the NS2 bullet. As you have programming experience, you should find this lua coding pretty easy

DaanVanYperen

The typical way to do this seems to be supplying my own AlienTeam.lua file copy with just small bits changed, which will make the mod more fragile and harder to maintain. I rather just replace a single local function from my own source files, but I can't seem to do that without also copying over the calling class functions.

I saw there is a way of injecting local variables into a class method, is there some way to inject local functions? (Specifically AssignPlayerToEgg into AlienTeam:Update).

Feha

How I usually do it:

local oldOnDestroy
oldOnDestroy = Class_ReplaceMethod( "Player", "OnDestroy",
function(self)
if Client and self.waterCinematic then
Client.DestroyCinematic(self.waterCinematic)
self.waterCinematic = nil
end

oldOnDestroy(self)
end
)

EDIT:
Oh, didnt read carefully enough and missed that you were talkign about *local* functions.
Class_ReplaceMethod obviously replaces a class-method, not local ones. Person8880 points to the correct function to use in your case (further down this page).

Soul_Rider

Best to use the hooking system for that. I don't have any experience, as I've always made full game mods rather than simply hooking files, but that will provide you with everything you need.

GhoulofGSG9

First i think i would go another way to change eegclass. Look into Hive:UpdateSpawnEgg()

Edit: Ok i memorized the function of ReplaceLocals( Function, TableOfLocals ) in a wrong way. Person8880 is totally right.

Rio

You could copy the whole AlienTeam.lua and change the local functions into non-local functions which you then can override. The downside is, that you have to replace your AlienTeam.lua everytime there is an update for NS2.

Person8880

You can override local functions. In fact, there's a premade function in core/lua/Class.lua that does it very easily.

ReplaceLocals( Function, TableOfLocals )

So in your case,

ReplaceLocals( AlienTeam.Update, { AssignPlayerToEgg = YourReplacementHere } )

McGlaspie

Pay attention to what Lua VM you're replacing those in. If the original function is declared in Server VM scope only, calling ReplaceLocals in the Client VM scope will toss errors.

If you're really using the modding framework, then your files are almost certainly mixed vm scopes. So, to make it easier, just wrap a "if Client" or "if Server" , etc. conditional block around the ReplaceLocals call.

DaanVanYperen

Ohhh thanks a lot guys! That'll clean things up right quick!

MCMLXXXIV

Wow, that override locals function would have been so handy for us! Better than the method which I'd suggest and which we used in Xenoswarm/Combat.

DaanVanYperen

Just a quick addition for anyone needing to get a reference for a nested local function.

Iin my case, I needed to replace local function AssignPlayerToEgg, called by local function updateAlienSpectators, called by class method AlienTeam.Update.

Added the function GetLocalFunction to get a reference to updateAlienSpectators

-- Retrieve called local function
-- Useful if you need to override a local function in a local function with ReplaceLocals but lack a reference to it.
function GetLocalFunction(originalFunction, localFunctionName)

    local index = 1
    while true do
        
        local n, v = debug.getupvalue(originalFunction, index)
        if not n then
           break
        end
            
        if n == localFunctionName then
            return v
        end
            
        index = index + 1
            
    end
    
    return nil
    
end

After that just a question of calling ReplaceLocals.

local updateAlienSpectators = GetLocalFunction(AlienTeam.Update, 'UpdateAlienSpectators')
ReplaceLocals( updateAlienSpectators, { AssignPlayerToEgg = AssignPlayerToEgg } )

Not sure this is the best way, but it works for me!

GhoulofGSG9

DaanVanYperen wrote: »

Just a quick addition for anyone needing to get a reference for a nested local function.

Iin my case, I needed to replace local function AssignPlayerToEgg, called by local function updateAlienSpectators, called by class method AlienTeam.Update.

Added the function GetLocalFunction to get a reference to updateAlienSpectators

-- Retrieve called local function
-- Useful if you need to override a local function in a local function with ReplaceLocals but lack a reference to it.
function GetLocalFunction(originalFunction, localFunctionName)

    local index = 1
    while true do
        
        local n, v = debug.getupvalue(originalFunction, index)
        if not n then
           break
        end
            
        if n == localFunctionName then
            return v
        end
            
        index = index + 1
            
    end
    
    return nil
    
end

After that just a question of calling ReplaceLocals.

local updateAlienSpectators = GetLocalFunction(AlienTeam.Update, 'UpdateAlienSpectators')
ReplaceLocals( updateAlienSpectators, { AssignPlayerToEgg = AssignPlayerToEgg } )

Not sure this is the best way, but it works for me!

Hmm GetLocalFunction reminds me of Shine.GetUpValue. But BTT yes this is probably the same way i would do it.

DaanVanYperen

@GhoulofGSG9 Yeah it's basically a stripped version of ReplaceLocals that just fetches the requested Upvalue.

I saw you post about Shine before. I'm simply too fresh in the whole modding process to be knowledgeable about the optional frameworks out there. One week in, still finding my way around Lua and vanilla NS2 code. I already have enough rope to hang myself with

Don't get me wrong. Some of the mods out there have been great study material. Xenoswarm's code for example is elegantly written and easy to learn from. It just addresses really common issues, I wouldn't have known what to search for with the upvalue fetching thing.

GhoulofGSG9

Ah you're fine, using sewleks framework as you do is the best way to go for a new gamemode, which "just" wants to changes some of the basic ns2 gameplay but keep alot ns2 stuff.