There are plenty of scripting possibilities for Transport Fever 2. Beside the functions in other game resources like constructions, there are some general possibilities:

• runFn function in mod.lua is a function that is called when the mod is loaded.
• postRunFn function in mod.lua is a function that is called after the runFn of all activated mods ran at least once and the other resources are loaded.
• Game scripts that are callback based and used ingame.
• Missions as specialized game scripts with indicated tasks to fulfill.

The two basic functions are described below.

The main file of every mod is mod.lua. This file contains the mod's metadata as well as the functions that are executed when the game is initialized. The general properties are described in mod components documentation.

function data()
return {
  -- metadata
  info = {
     -- Properties as described in Mod Components
     -- Mod Parameters: (optional)
     params =  { ... } 
  },
 
  -- additional options to show in the advanced game settings menu (optional)
  options = {
    terrain = { { "test1", _("Test entry 1") }, ... },
  },
 
  -- main function before resource loading (optional)
  runFn = function (settings, modParams)
    -- put your code here!
  end, 
 
  -- additional function after resource loading (optional)
  postRunFn = function (settings, params)
    -- put your code here!
  end,
}
end

All scripting possibilities in the mod.lua are optional and can be omitted if not needed.

Mods can provide individual parameters in the params property of the info block. These use the parameter types that are available for constructions too. The user can select his preferences in the advanced settings when creating a new game or loading an existing savegame. Parameters of all mods are available in the runFn function described below.

The options block enables mods to add additional values to the advanced game option categories provided by the game:

• climate contains a list of available climates.
• vehicles contains a list of available vehicle sets.
• nameList contains a list of available town name sets.
• environment contains a list of available environments.
• difficulty contains a list of difficulty levels.

The initial set of options (and the base run functions) are defined in res\config\base_mod.lua. To add additional options in one of the categories, a list can be added to the options block with the category as the key. Eack element of the list consists of two values:

1. the option identifier that will be provided to the runFn.
2. the text that should be displayed in the dropdown.

The main function that is called when a mod is loaded is the runFn function. It receives two parameters:

• settings containing the list of option categories and the chosen option identifiers.
• modParams a list of all mod parameters with the mod id as key of the list items. To retrieve the list of parameters for the current mod, modParams[getCurrentModId()] can be used.

What is done with these parameters is up to the mod. There are multiple ways how a mod can do its work:

• Config variables: the game configuration can be changed directly by setting the appropriate values in the configuration table.
• File filter: a function that is invoked for all files in a directory. The function can then decide whether the file should be included or not. The file filter can access the data in the file, making it a very versatile tool.
• Modifier: a function that is invoked after a resource file has been loaded. It is used for modifying the data on the fly.

See the following pages for information on game configs, resource modifiers and file filters.

The postRunFn function is called once after all resources are loaded. It receives two parameters:

• settings containing the list of option categories and the chosen option identifiers.
• modParams a list of all mod parameters with the mod id as key of the list items. To retrieve the list of parameters for the current mod, modParams[getCurrentModId()] can be used.

It is possible to use script functions provided by the Scripting API, e.g. it is possible to add additional multiple unit configurations or construction modules based on the loaded resources.

The base_mod.lua contains an exemplaric postRunFn function that dynamically adds track modules for all loaded track types.

postRunFn = function(settings, params)
  -- fetch all loaded track types from the track types repository
  local tracks = api.res.trackTypeRep.getAll()
 
  -- iterate over the list and do for each of the track types
  for __, trackName in pairs(tracks) do
 
    -- initialize a new module
    local mod = api.type.ModuleDesc.new()
 
    -- fetch the data for the current track type
    local track = api.res.trackTypeRep.get(api.res.trackTypeRep.find(trackName))
 
    -- exclude the vanilla track types as there are already trackmodules for them
    if trackName ~= "standard.lua" and trackName ~= "high_speed.lua" then 
 
      -- generate two modules per tracktype, one without and one with catenary
      for __, catenary in pairs({false, true}) do
 
        -- mimic a fileName
        mod.fileName = "trainstation_" .. tostring(trackName) .. (catenary and "catenary" or "")
 
	...
 
        -- add description and an icon reference		
	mod.description.name = track.name .. (catenary and _(" with catenary") or "")
	mod.description.description = track.desc .. (catenary and _(" (with catenary)") or "")
	mod.description.icon = track.icon
	if mod.description.icon ~= "" then
	  mod.description.icon = string.gsub(mod.description.icon, ".tga", "")
	  mod.description.icon = mod.description.icon .. "_module" .. (catenary and "_catenary" or "") .. ".tga"
        end
 
        ...
 
        -- provide functions for ''updateFn'' and ''getModelsFn'' 				
        mod.updateScript.fileName = "construction/station/rail/modular_station/trackmodule.updateFn"
        mod.updateScript.params = {
	  trackType = trackName,
	  catenary = catenary
        }
        mod.getModelsScript.fileName = "construction/station/rail/modular_station/trackmodule.getModelsFn"
        mod.getModelsScript.params = { 
          trackType = trackName,
	  catenary = catenary
        }
 
        -- add the new module definition to the module repository			
        api.res.moduleRep.add(mod.fileName, mod, true)
      end
    end
  end
end