Dependencies#

Reading and writing from native collections requires maintaining a delicate chain of dependencies.
Systems take dependencies in, and output them. Collections should not be accessed without relying on those dependencies.

Resolution#

Other exceptions may lead to dependency errors, so be careful to resolve the easiest ones first!
Errors thrown immediately after this error can be the root cause.

Utilise JobHandles#

Feed the system's handle (state.Dependency) into the first thing that requires something complete before it runs.
Whatever receives a JobHandle should return its own, and you create a chain of these dependencies which must ultimately be set back to the system's handle.

Verify dependencies in value types are modified#

If you are passing around a SystemState, make sure it's passed by ref so modifications to its dependency actually update across systems.

Do not read from collections before dependencies are evaluated#

Ensure you don't use any properties of a native collection (like .Length) before you have waited on a dependency. In the case of an EntityQuery, you should use CalculateEntityCount to get the length of an array without requiring a dependency.

In some cases you can use a job interface like IJobParallelForDefer, which does not rely on Length being provided before execution.