Traits

Traits define the behavior of entities by operating on entities that contain specific Pieces. They act as systems that process and modify entity states dynamically.

Understading them

A Trait is executed whenever an entity matches the required Pieces specified in its query.

local Query = Prism.Query { query = function() return health end }

local counting = 1

Query:trait('Regenerate Health', function(data, health)
    print('This is the', counting, 'time')
    counting += 1
end)

Registry:include { Query }

Registry:add(entity, health)
--> This is the 1 time

If the entity no longer meets the requirements, the trait is removed. If it later meets the conditions again, the trait is reapplied.

Registry:remove(entity, health)

Registry:add(entity, health)
--> This is the 2 time

Trait Cleanup

Traits can be added or removed dynamically, but removing a trait does not automatically revert changes. You must manually handle the cleanup of any data associated with it.

return Prism.Query {
    query = function()
        return part
    end
}

:trait('Create part', function(data, part)
    local instance = Instance.new('Part')

    -- Store the instance for cleanup when the trait is removed
    table.insert(data.cleaning, instance)

    part.data.instance = instance
end)

Modular Code

Returning queries from modules allows for a cleaner codebase. From now on, we will follow this approach.

Trait Execution Order

A single query can have multiple traits. Traits are executed in the order they are defined within the query.

return Prism.Query {
    query = function()
        return part
    end
}
:trait('Create part', function(data, part)
    local instance = Instance.new('Part')

    -- Store the instance for cleanup when the Trait is removed
    table.insert(data.cleaning, instance)

    part.data.instance = instance
end)

:trait('Print part', function(data, part)
    print(part.data.instance)
    --> 'Part'
end)