Component System Overview

What is a Component?

Components are modular pieces of functionality that can be attached to units to give them specific capabilities. Rather than building units through inheritance, you compose them from components.

Component-Based Architecture Benefits

  • Modularity - Each component handles one responsibility
  • Reusability - Use the same components on different unit types
  • Flexibility - Mix and match components to create varied units
  • Testability - Components can be tested independently
  • Performance - Only required components are active

Base Component Class

All components extend from the base class RTS_Component, which always has a reference to its entity (usually the parent).

func fetch_entity() -> RTS_Entity:
    return get_parent() as RTS_Entity

and can be turned on and off:

func set_component_inactive():
    component_is_active = false

func set_component_active():
    assert(!component_is_active,"RTS_Component set active twice. You're game logic is probably flawed.")
    component_is_active = true

If not required otherwise, leaving set_component_active_on_ready set to true is usually the right choice.

RTS_Component is the main building block for creating modular and scalable, yet unique entity behaviors. For developers wanting to adopt this framework, it is recommended to create your own unique components which add features and complexity to entities by extending this base class.

Here we briefly introduce the most common components that are included in the RTS Entity Controller. Note that RTS_Ability and many other scripts (such as RTS_Weapon) also inherit from RTS_Component.

Common Components

Selection & Interaction

Movement & Navigation

Health & Combat

Visuals & Animation

  • VisualComponent - Rendering and visibility
  • [AnimationTreeComponent] - AnimationTree and AnimationPlayer integration. Also see Attack System

Example: ExampleUnit.tscn

As alluded to in Entity System, components usually (but not always) sit as direct children underneath the entity:

ExampleUnit (RTS_Entity)
├── (...)
├── SelectableComponent
├── MovableComponent
├── HealthComponent
├── DefenseComponent
├── AnimationTreeComponent

Creating Custom Components

Creating custom components is as easy as inheriting from RTS_Component. The easiest thing to forget is to properly implement 

func set_component_inactive()
func set_component_active()

so that components can be turned off which should disable any heavy computation or update loops.

Next Steps