jecs/docs/api/query.md
2024-07-26 04:36:30 +02:00

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# Query
A World contains entities which have components. The World is queryable and can be used to get entities with a specific set of components.
## Functions
### new()
```luau
function World.new(): World
```
Creates a new world.
Example:
::: code-group
```luau [luau]
local world = jecs.World.new()
```
```ts [typescript]
import { World } from "@rbxts/jecs";
const world = new World();
```
:::
## entity()
```luau
function World:entity(): Entity -- The new entit.
```
Creates a new entity.
Example:
::: code-group
```luau [luau]
local entity = world:entity()
```
```ts [typescript]
const entity = world.entity();
```
::
:
### component()
```luau
function World:component<T>(): Entity<T> -- The new componen.
```
Creates a new component.
Example:
::: code-group
```luau [luau]
local Health = world:component() :: jecs.Entity<number>
```
```ts [typescript]
const Health = world.component<number>();
```
:::
::: info
You should use this when creating components.
For example, a Health type should be created using this.
:::
### get()
```luau
function World:get(
entity: Entity, -- The entity
...: Entity<T> -- The types to fetch
): ... -- Returns the component data in the same order they were passed in
```
Returns the data for each provided type for the corresponding entity.
:::
### add()
```luau
function World:add(
entity: Entity, -- The entity
id: Entity<T> -- The component ID to add
): ()
```
Adds a component ID to the entity.
This operation adds a single (component) id to an entity.
::: info
This function is idempotent, meaning if the entity already has the id, this operation will have no side effects.
:::
### set()
```luau
function World:set(
entity: Entity, -- The entity
id: Entity<T>, -- The component ID to set
data: T -- The data of the component's type
): ()
```
Adds or changes the entity's component.
### query()
```luau
function World:query(
...: Entity<T> -- The component IDs to query with. Entities that satifies the conditions will be returned
): Query<...Entity<T>> -- Returns the Query which gets the entity and their corresponding data when iterated
```
Creates a [`query`](query) with the given component IDs.
Example:
::: code-group
```luau [luau]
for id, position, velocity in world:query(Position, Velocity) do
-- Do something
end
```
```ts [typescript]
for (const [id, position, velocity] of world.query(Position, Velocity) {
// Do something
}
```
:::