DOTS-Stats is a high performance and scalable Stats-System.

• Maximum flexibility. Thanks to the pure component approach, it allows you to implement abilities, items, buffs, potions and make them work together as one single thing.
• High performance. Zero GC allocations.
• 100% ECS-ish. No more complex abstact OOP classes that work here but don't work there.
• Ready-made base Authoring components for customization in the editor
• Supports multiplying and additive stats
• The minimum amount of boilerplate code.
• Compatible with burst.
• Compatible with il2cpp.

Min. Requirements: Unity >= 2019.4.18 and entities package >= 0.11.2-preview.1

Tested on: Unity 2020.2.3 and entities package 0.17.0-preview.42

You can install the repository using UPM: Just add this line in Packages/manifest.json:

"com.nanory.unity.entities.stats": "https://github.com/SinyavtsevIlya/DOTS-Stats.git",

Let's say you want to create an RPG'like stats system. When the player takes a weapon, his Attack stat grows. When he drops it, the stat returns to default.

public struct Attack : IComponentData
{
    // The only constraint is you must have a float field. 
    public float Value; 
}

public class AttackAuthoring : StatAuthoringBase<Attack>
{
    [SerializeField] float _value;
    // Simply return a new instance of "Attack" and set it's value from the serialized field. 
    protected override Attack GetStat() => new Attack() { Value = _value };
}

You'll get this:

And also add a StatReceiverTagAuthoring on the Player gameobject, to make him a "Stat-Reciever". (means that he able to accumulate stats from other contexts, e.g. items, buffs etc.)

Don't forget to add a ConvertToEntity on them to enable automatic conversion in a scene.

// anywhere you want. Say on spacebar hit:
EntityManager.SetStatsChanged(swordEntity, playerEntity);

// and call this to deequip:
EntityManager.SetStatsRemoved(swordEntity);

    [UpdateInGroup(typeof(StatSystemGroup))]
    public class CalculateAttackSystem : CalculateStatSystem<Attack> { }

You also able to add a system in a shorter way:

DefaultWorldInitialization.AddSystemsToRootLevelSystemGroups(_world, typeof(CalculateStatSystem<Attack>))

This step is recomended to be automated (code-gen, code-snippets, build processors or whatever you like)

Thats it!

Sure. Just use EnityCommandBuffer versions of extension methods:

entityCommandBuffer.SetStatsChanged(contextEntity, statReceiverEntity);
entityCommandBuffer.SetStatsRemoved(contextEntity);

Just add a StatRecievedElementEvent component in your querry. Here is an example:

 Entities
    .ForEach((Entity ownerEntity, DynamicBuffer <StatRecievedElementEvent> statRecievedEvents, StatsWidget widget) =>
    {
        for (var idx = 0; idx < statRecievedEvents.Length; idx++)
        {
            var statRecievedEvent = statRecievedEvents[idx];

            if (statRecievedEvent.Is<Attack>())
                widget.SetAttack(EntityManager.GetComponentData<Attack>(ownerEntity).Value);

            if (statRecievedEvent.Is<AttackSpeed>())
                widget.SetAttackSpeed(EntityManager.GetComponentData<AttackSpeed>(ownerEntity).Value);
                
            // more stats here...
        }
    });

Since several stats can change at once during one frame, the event is presented as a DynamicBuffer of structs that clears automatically in the end of frame.