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Last Update: 2023-07-06

Component

Components are functional modules attached to entities to provide specific behaviors and properties.

Overview​

The component system is a key part of Don't Starve Together's entity-component architecture. Components encapsulate specific functionality that can be added to entities, making them modular and reusable. Each component handles a specific aspect of an entity's behavior or properties.

Component Structure​

A typical component has this structure:

local MyComponent = Class(function(self, inst)
    self.inst = inst
    self.value = 100
    self.enabled = true
end)

function MyComponent:OnSave()
    return {
        value = self.value,
        enabled = self.enabled
    }
end

function MyComponent:OnLoad(data)
    self.value = data.value or self.value
    self.enabled = data.enabled or self.enabled
end

function MyComponent:GetDebugString()
    return string.format("Value: %d, Enabled: %s", self.value, tostring(self.enabled))
end

function MyComponent:DoSomething(amount)
    if self.enabled then
        self.value = self.value + amount
        self.inst:PushEvent("valueupdated", {value = self.value})
    end
end

return MyComponent

Component Lifecycle​

Components have several lifecycle methods:

  • Constructor: Called when the component is created
  • OnRemoveFromEntity: Called when the component is removed
  • OnSave: Called when the game is saving
  • OnLoad: Called when the game is loading
  • GetDebugString: Called when debugging information is requested

Adding Components to Entities​

Components are added to entities like this:

entity:AddComponent("health")
entity.components.health:SetMaxHealth(100)

-- Check if entity has a component
if entity.components.combat then
    entity.components.combat:SetDefaultDamage(10)
end

-- Remove a component
entity:RemoveComponent("burnable")

Common Components​

Here are some important components in Don't Starve Together:

  • health: Handles entity health and damage
  • hunger: Manages hunger for characters
  • sanity: Controls sanity level for characters
  • inventory: Manages item storage
  • combat: Handles attacking and combat
  • lootdropper: Determines what items an entity drops when killed
  • inspectable: Allows an entity to be inspected
  • workable: Makes an entity workable with tools
  • burnable: Makes an entity able to burn
  • propagator: Allows an entity to spread fire
  • stewer: For cooking food items
  • growable: For things that grow over time
  • trader: For entities that can trade
  • locomotor: Handles movement

Component Replication​

For multiplayer, components need to replicate their state between server and clients:

-- In component initialization
if TheWorld.ismastersim then
    -- Server-only initialization
    self.netvar = net_bool(self.inst.GUID, "mycomponent.value", "valuedirty")
end

-- Server setting a value
function MyComponent:SetValue(val)
    self.value = val
    self.netvar:set(val)
end

-- Client listening for changes
if not TheWorld.ismastersim then
    inst:ListenForEvent("valuedirty", OnValueChanged)
end
  • Entity system
  • Network replication
  • Event system
  • Save/load system