56 lines
1.7 KiB
Markdown
56 lines
1.7 KiB
Markdown
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# Entity
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The `Entity` class is a simplistic data structure that contains only two
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properties: a semi-unique identifier and a collection of components. It is
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immutable and thread-safe.
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## Identifier
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Creating a new entity without any parameters will assign a new id, this is
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currently implemented as an `int` that is initialized by a static property
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managed by the `Interlock` to make it a thread-safe operation.
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```csharp
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Entity entity = new();
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```
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_NOTE: This means there is an effective limitation of 4.3 billion entities. The
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current reasoning is that most games don't need to have that many concurrent
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objects and will rarely roll over._
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In situations were a more custom identifier management is needed, one of the
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constructors takes the `int` as a parameter.
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```csharp
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var idManager;
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Entity entity = new(idManager.GetNext());
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```
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In addition, there is a copy constructor that takes another entity and copies
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both the identifier and the components of the entity.
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```csharp
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Entity entity1 = new();
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Entity entity2 = new(entity1);
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Assert.Equal(entity1.Id, entity2.Id);
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```
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## Components
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In addition to the identifier, entities have a collection of components. This is
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exposed as an immutable collection. Adding, removing, and setting components are immutable operations that create a new `Entity` object with the same identifier and a new collection of components.
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```csharp
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Entity entity1 = new();
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Entity entity2 = entity1.Add(23).Add("string value");
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Entity entity3 = entity2.Set(56);
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Assert.Equal(entity1.Id, entity2.Id);
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Assert.Equal(entity1.Id, entity3.Id);
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Assert.Equal(2, entity2.Components.Count);
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Assert.Equal(2, entity3.Components.Count);
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Assert.Equal(23, entity2.Get<int>());
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Assert.Equal(56, entity3.Get<int>());
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```
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