Question Can someone show me how to use ComponentDataFromEntity<T> correctly.

I'm still a novice in writing ecs code and I just watch tutorial videos on youtube to learn but those all are quite dated now. I used ComponentDataFromEntity<T> in my code and in the console it kept showing the error which is "InvalidOperationException: <>c__DisplayClass_OnUpdate_LambdaJob0.JobData.datas is not declared [ReadOnly] in a IJobParallelFor job. The container does not support parallel writing. Please use a more suitable container type". Can anyone show me some right example using ComponentDataFromEntity<T> in a system please.

 

You can't use vanilla ComponentDataFromEntity<T> in parallel. Use Schedule() in your ForEach(). Another way is to add WithReadOnly(componentDataFromEntity) description to your ForEach().

Optionally, you could also create the struct job yourself. You can then set the attribute [NativeDisableParallelForRestriction] to the ComponentDataFromEntity<T> variable. This is kind of a hack. You have to make sure that no more than a single thread will read/write an item in ComponentDataFromEntity. If you're only reading from your ComponentDataFromEntity, then add the [ReadOnly] attribute so you can safely use it with parallel threads.

 

You can also disable the parallel for restriction in lambda job using

.WithNativeDisableParallelForRestriction(variable)