Idiomatic way to wait for component availability

[dire bear]

I often have systems, that wait for a singleton, that is created during baking. I want to cache that singleton, so I do not have to check in every update if it is available yet.

I have it as a private member in the ISystem struct, and I have state.RequireForUpdate<ThatComponent>(); in my OnCreate Method.

I thought that should be enough to delay OnUpdate until it is available.

Often that does not work, so I will check in the OnUpdate with a call to System.Api.TryGetSingleton<ThatComponent>(out _cachedComponent)) but that seems uncessary resource heavy.

Is there a correct way to do that?

[feral flare]

RequireForUpdate should be enough
if any of my systems call onupdate ignoring requires it will crash instantly

[ornate rover]

Require for update is fine, just not though it doesn't use filters so it doesn't care about enabled state etc

If it exists regardless if it's disabled it'll run

[summer anvil]

If you do SystemAPI.GetSingleton<ThatComponent>() then state.RequireForUpdate<ThatComponent>() will always work. Do you have an example of a time it didn't? Because you might've done something wrong

[ornate rover]

Make it an enable component and disable it

System will run, get singleton will return nothing

[summer anvil]

ah, true, though I don't think you should ever make a singleton an Enablable component? It's not like you save any space on it

[ornate rover]

It can be useful

But yes you just need to be aware of how filters work

[dire bear]

But the get Singleton would be in the update method, so no caching, right? Is that performant?

[elfin reef]

you can always use the profiler to check how much time a system update requires.

Also Unity ECS is built around value types so caching doesn't help you in general.