[Question] How to implement string-based data loading (lookup ID by name)?

[talesmm14]

Hi,

I am migrating a project from Concord to evolved.lua and I rely heavily on data-driven loading from files (JSON/Lua tables).

In Concord, I have a generic loader that iterates over keys (strings) and maps them directly to components, like this:

-- My current workflow in Concord
function loadEntitiesFromFile(world, entities)
    for _, entityData in ipairs(entities) do
        local e = Concord.entity(world)
        for component_name, params in pairs(entityData) do
            -- "component_name" is a string (e.g., "position")
            -- Concord resolves this string to the component class automatically
            if type(params) == "table" then
                e:give(component_name, unpack(params))
            else
                e:give(component_name, params)
            end
        end
    end
end

In evolved.lua, Fragments are IDs generated at runtime.

My Question:
Is there a built-in mechanism or a helper function to retrieve a Fragment ID by its string name?

For example, if I define a fragment using the builder:

local Position = evolved.builder():name("position"):build()

Is there something like evolved.find_by_name("position") that returns the ID? Or is the only solution to manually maintain a global Table<String, ID> registry to map the file keys to the fragment IDs?

I am looking for a way to keep my generic loader working without hardcoding every single component mapping manually.

Thanks!

[BlackMATov]

Hi!

Currently, the library does not have a built-in mechanism to retrieve fragments by their names. The evolved.NAME fragment trait is only used for debugging purposes and does not create any internal mapping from names to IDs. So if you want to retrieve fragment IDs by their names, you will need to maintain your own mapping table.

However, I think this is a common use case, and I am considering adding such a feature. I will explore the best way to implement it, taking into account that names are not guaranteed to be unique. My initial thoughts are to add two new functions:

lookup: string -> entity?
multi_lookup: string -> entity[], integer

For now, you will need to maintain your own mapping table, unfortunately. I will keep this issue open to update you on the progress of this feature. Thank you for the suggestion!

P.S.
Don't forget to use builders to spawn your entities because giving fragments one by one is very inefficient and leads to a lot of structural changes.

[talesmm14]

Hi!

Currently, the library does not have a built-in mechanism to retrieve fragments by their names. The evolved.NAME fragment trait is only used for debugging purposes and does not create any internal mapping from names to IDs. So if you want to retrieve fragment IDs by their names, you will need to maintain your own mapping table.

However, I think this is a common use case, and I am considering adding such a feature. I will explore the best way to implement it, taking into account that names are not guaranteed to be unique. My initial thoughts are to add two new functions:

lookup: string -> entity?
multi_lookup: string -> entity[], integer

For now, you will need to maintain your own mapping table, unfortunately. I will keep this issue open to update you on the progress of this feature. Thank you for the suggestion!

P.S. Don't forget to use builders to spawn your entities because giving fragments one by one is very inefficient and leads to a lot of structural changes.

I tried to implement something based on the ugly code I wrote today to solve the problem in my project, could you take a look? Pull request

[BlackMATov]

Just wait for a few days, I already have some ideas for this feature and will implement it soon :-)

[BlackMATov]

Here it is! The dev branch at your service :-)