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179 |An entity component system made with typescript for usage in the Nova Engine.
69 |npm i --save @nova-engine/ecs
71 | To use the entity component system, you first must create your Engine to store your systems and entities.
74 |You can create as many as you wish, but usually it's only one per application.
75 |import { Engine } from "@nova-engine/ecs";
76 | const engine = new Engine();
77 | Now you just define your components:
79 |import { Component } from "@nova-engine/ecs";
80 |
81 | // Components can have custom constructors, but they must be able to be initialized
82 | // with no arguments, because entities creates the instances for you.
83 | // Try not to save complex data types in yout components
84 | class PositionComponent implements Component {
85 | x = 0;
86 | y = 0;
87 | }
88 |
89 | class VelocityComponent implements Component {
90 | x = 0;
91 | y = 0;
92 | }
93 |
94 | // If you are making a component library, and want to avoid collitions
95 | // You can add a tag to your component implementations
96 |
97 | class MyLibraryComponent implements Component {
98 | // This will ensure your component won't collide with other "MyLibraryComponent"
99 | static readonly tag = "my-library/MyLibraryComponent";
100 | }
101 | You can also define your systems:
103 |import { Component, Family, System, FamilyBuilder } from "@nova-engine/ecs";
104 | class GravitySystem extends System {
105 | static readonly DEFAULT_ACCELERATION = 0.98;
106 | family?: Family;
107 | acceleration: number;
108 |
109 | // Constructors are free for your own implementation
110 | constructor(acceleration = GravitySystem.DEFAULT_ACCELERATION) {
111 | super();
112 | this.acceleration = acceleration;
113 | // higher priorities means the system runs before others with lower priority
114 | this.priority = 300;
115 | }
116 | // This is called when a system is added to an engine, you may want to
117 | // startup your families here.
118 | onAttach(engine: Engine) {
119 | // Needed to work properly
120 | super.onAttach(engine);
121 | // Families are an easy way to have groups of entities with some criteria.
122 | this.family = new FamilyBuilder(engine).include(VelocityComponent).build();
123 | }
124 |
125 | // This, in reality is the only method your system must implement
126 | // but using onAttach to prepare your families is useful.
127 | update(engine: Engine, delta: number) {
128 | for (let entity of this.family.entities) {
129 | // Easy to get a component by class
130 | // Be warned, if the entity lacks this component, an error *will* be thrown.
131 | // But families ensures than we will always have the required components.
132 | const velocity = entity.getComponent(VelocityComponent);
133 | velocity.y += this.acceleration;
134 | // if the family doesn't require that component
135 | // you can always check for it
136 | if (entity.hasComponent(PositionComponent)) {
137 | const position = entity.getComponent(PositionComponent);
138 | } else {
139 | // You can create components on an entity easily.
140 | const position = entity.putComponent(PositionComponent);
141 | }
142 | }
143 | }
144 | }
145 | You can only have one instance of a component per entity. 148 | entity IDs are not generated by default, if you need them to have IDs, set them up yourself:
149 |entity.id = myGeneratedId();
150 | The license is Apache-2.0, so use it as you please without worries.
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256 |Computes a list of entities on the family. 132 | The list may or may not be cached, depending of implementation.
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180 |
A family is a criteria to separate your entities. 76 | You can have families on wich entities must have a component, 77 | entities cannot have some components or a mix of both. 78 | Families also cache the entities of the engine by default, 79 | so you won't have to worry about filtering entities every time.
80 |