encompass-cs-docs/content/concepts/component.md

50 lines
1.5 KiB
Markdown

---
title: "Component"
date: 2019-05-22T12:51:29-07:00
weight: 5
---
A Component is a structure of related data.
To define a Component, declare a struct which implements the **IComponent** interface.
```cs
using Encompass;
using System.Numerics;
public struct VelocityComponent : IComponent {
public Vector2 Velocity { get; }
public VelocityComponent(Vector2 velocity)
{
Velocity = velocity;
}
}
```
Components are attached to Entities with the **SetComponent** method.
```cs
using Encompass;
...
var worldBuilder = new WorldBuilder();
var entity = worldBuilder.CreateEntity();
worldBuilder.SetComponent(entity, new VelocityComponent(Vector2.One));
```
**SetComponent** can also be used from within an **Engine**. We will talk more about this later.
Components are always structs, meaning they follow value-type semantics. If you are used to working with classes you might find this confusing.
One major point of difference is that value types are _copied_ rather that passed by reference by default.
You can read more about value types here: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/value-types
If you use them idiomatically, you don't have to worry about them creating garbage collection pressure, so this is a big win for performance when working in C#.
{{% notice warning %}}
Components should **never** reference other Components directly. This breaks the principle of loose coupling. You **will** regret it if you do this.
{{% /notice %}}