How to add a function to a metatable?

Thalassicus · Apr 2, 2012

I have a function:

PHP:

function Player_ChangeYieldStored(player, yieldType, yield)

I'd like to make it like this:

PHP:

function Player:ChangeYieldStored(yieldType, yield)

Is this possible, and if so, how?

Pazyryk · Apr 2, 2012

See Lua documentation here.

I have no idea whether Civ5 has put setmetatable and getmetatable off-limits, however.

Pazyryk · Apr 2, 2012

OK, did some testing and... yes, you can.

player has a metatable with one key, "__index", which itself is a table of functions:

> print(Players[0])
EaMain: table: 15495B78
> print(getmetatable(Players[0]))
EaMain: table: 15498C10
> for key, value in pairs(getmetatable(Players[0])) do print(key, value) end
EaMain: __index table: 1549A5D8
> print(getmetatable(Players[0]).__index)
EaMain: table: 1549A5D8
> for key, value in pairs(getmetatable(Players[0]).__index) do print(key, value) end

Spoiler :

You can add to .__index easily enough:

> a = getmetatable(Players[0]).__index
> print(a)
EaMain: table: 1549A5D8
> a.Pazprint = function() print("Paz is Great!") end
> Players[0].Pazprint
function: 14816388
> Players[0].Pazprint()
EaMain: Paz is Great!
> Players[0]

azprint()
EaMain: Paz is Great!
> Players[1]

azprint()
EaMain: Paz is Great!
> Players[22]

azprint()
EaMain: Paz is Great!

You can see above that all player objects use the same metatable.

Thalassicus · Apr 2, 2012

Thank you! :goodjob:

Thalassicus · Apr 15, 2012

How can we get the plot metatable before the map is created, or the city metatable before cities exist? The metatables exist... we just need to get a pointer to them. :think:

whoward69 · Apr 15, 2012

Thalassicus said:
How can we get the plot metatable before the map is created? Map.GetPlotByIndex(0) returns nil when map scripts have not yet run. This is a similar problem to getting the city metatable when no cities exist yet...

Unless it's been changed recently, you can't - as the 8 "types" all suffer from lazy initialisation (so until some code has actually used "one" the control structures don't exist, and if you don't have any cities you can't use "one")

See http://forums.2kgames.com/showthrea...lection-for-Lua-objects&p=1408725#post1408725

Thalassicus · Apr 15, 2012

Thank you for that information. I'm glad we can create some things in the class:method() format... the player, team, and static classes. That's better than nothing!

Hopefully the player class is enough to get changes from my yield library to show up in other mods. InfoAddict mostly shows player-level data... hmm... :think:

whoward69 · Apr 15, 2012

Thalassicus said:
Thank you for that information... so we can only add methods to the player, team, and static classes. Well, at least we can do some things as class:method instead of standalone functions. I'd converted my standalone player and static class methods, then noticed the issue when I got to the plot class.

No, you can add to the Plot and City objects but only after any plot object or any city object has been used for the first time.

You'll just need to get creative about when you try to add your methods to the metadata table - you won't be able to do it in file scope code. You'll need to hook an event that fires when an object is used (or after you know that objects are available), access any object of that type (to force the lazy initialisation to run) and then add the methods to the metadata. For good measure the OnEventCallback() can then "unhook" itself (Events.Whatever.remove(OnEventCallback) as this now works correctly)

Thalassicus · Apr 15, 2012

I see what you mean... hmm. So for example, if I want a plot:GetID() function, it can't be in a file included in map scripts? This gives me two options:

Find the right spot to insert each plot class method. This might take hours, but would make yieldlibrary compatible with any mods.
Add infoaddict to my project. This would take minutes, but would only allow compatibility with infoaddict.

I think I'll take a break and come back to it later with a fresh mind. Hours of regular-expression usage leaves me frazzled! :crazyeye:

whoward69 · Apr 16, 2012

You may be able to use Events.SequenceGameInitComplete (see LoadScreen.lua), as at that point GameInfo and Game.GetActivePlayer() are available, so I'm guessing the Map, Area, Plot, Team and Player objects are available. You should also have Units somewhere (or if not, you could add one to a CS/AI player and then destroy it).

Cities you should be able to get via OnCityCreated( hexPos, playerID, cityID, cultureType, eraType, continent, populationSize, size, fowState ) (see CityBannerManager)

Gedemon · Apr 20, 2012

Thank you all, this will be very usefull

How to add a function to a metatable?

Thalassicus

Bytes and Nibblers

Pazyryk

Deity

Pazyryk

Deity

Thalassicus

Bytes and Nibblers

Thalassicus

Bytes and Nibblers

whoward69

DLL Minion

Thalassicus

Bytes and Nibblers

whoward69

DLL Minion

Thalassicus

Bytes and Nibblers

whoward69

DLL Minion

Gedemon

Modder

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