50 lines
1.5 KiB
Markdown
50 lines
1.5 KiB
Markdown
---
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title: "Component"
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date: 2019-05-22T12:51:29-07:00
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weight: 5
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---
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A Component is a structure of related data.
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To define a Component, declare a struct which implements the **IComponent** interface.
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```cs
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using Encompass;
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using System.Numerics;
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public struct VelocityComponent : IComponent {
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public Vector2 Velocity { get; }
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public VelocityComponent(Vector2 velocity)
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{
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Velocity = velocity;
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}
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}
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```
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Components are attached to Entities with the **SetComponent** method.
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```cs
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using Encompass;
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...
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var worldBuilder = new WorldBuilder();
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var entity = worldBuilder.CreateEntity();
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worldBuilder.SetComponent(entity, new VelocityComponent(Vector2.One));
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```
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**SetComponent** can also be used from within an **Engine**. We will talk more about this later.
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Components are always structs, meaning they follow value-type semantics. If you are used to working with classes you might find this confusing.
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One major point of difference is that value types are _copied_ rather that passed by reference by default.
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You can read more about value types here: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/value-types
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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#.
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{{% notice warning %}}
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Components should **never** reference other Components directly. This breaks the principle of loose coupling. You **will** regret it if you do this.
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{{% /notice %}}
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