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47 lines
1.6 KiB
47 lines
1.6 KiB
# Zig ECS
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Zig ECS is a zig port of the fantasic [Entt](https://github.com/skypjack/entt). Entt is _highly_ templated C++ code which depending on your opinion is either a good thing or satan itself in code form. Zig doesn't have the same concept as C++ templates (thank goodness!) so the templated code was changed over to use Zig's generics and compile time metaprogramming.
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## What does a zigified Entt look like?
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Below are examples of a View and a Group, the two main ways to work with entities in the ecs along with the scaffolding code.
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Declare some structs to work with:
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```zig
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pub const Velocity = struct { x: f32, y: f32 };
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pub const Position = struct { x: f32, y: f32 };
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```
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Setup the Registry, which holds the entity data and is where we run our queries:
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```zig
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var reg = ecs.Registry.init(std.testing.allocator);
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```
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Create a couple entities and add some components to them
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```zig
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var entity = reg.create();
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reg.add(entity, Position{ .x = 0, .y = 0 });
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reg.add(entity, Velocity{ .x = 5, .y = 7 });
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...
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```
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Create and iterate a View that matches all entities with a `Velocity` and `Position` component:
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```zig
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var view = reg.view(.{ Velocity, Position }, .{});
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var iter = view.iterator();
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while (iter.next()) |entity| {
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const pos = view.getConst(Position, entity); // readonly copy
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var vel = view.get(Velocity, entity); // mutable
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}
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```
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The same example using an owning Group:
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```zig
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var group = reg.group(.{ Velocity, Position }, .{}, .{});
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group.each(each);
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fn each(e: struct { vel: *Velocity, pos: *Position }) void {
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e.pos.*.x += e.vel.x;
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e.pos.*.y += e.vel.y;
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}
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```
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