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

---
title: "Component"
date: 2019-05-22T12:51:29-07:00
weight: 5
---

A Component is a collection 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;
}
```

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 { velocity = Vector2.Zero });
```

**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. (Insert link about that here). If you use them idiomatically, you don't have to worry about them being garbage-collected.

{{% 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 %}}