Entities

Introduction

First see Entity Component System.

An entity without components doesn't do much, but has some important functionality:

• Every entity has a position in the world, which is measured in metres. This is used for rendering and physics.
• Every entity also has a scale which determines its size. This is used for rendering and physics.

Entity lifecycle

The entity lifecycle can be seen in the figure below.

TODO: Figure

Note that create() is not called when the entity is instantiated through new Entity(), but when the entity is added into the world. This means we know that an entity doesn't do anything while we are still adding components to it, or before we've placed it in the game.

Entities can also be disabled or enabled during gameplay. While an entity is disabled, it won't draw on the screen or run any updates. This is very useful when an entity isn't needed right now but will be later, since it won't have to be created twice. You can also create entities ahead of time but leave them disabled until they're necessary.