/// <summary>
/// Update system state. This causes the implementation of <see cref="Update(long, EntityQueryResult)"/> to
/// be called with a set of entities chosen based on the currently set filters, and the implementations
/// of <see cref="OnEntityAdded"/> and <see cref="OnEntityRemoved"/> to be called accordingly.
/// </summary>
/// <param name="elapsedTicks">The amount of ticks that elapsed since the last update</param>
public override void Update(long elapsedTicks)
{
// Retrieve new query result containing all entities that satisfy the current filter
var result = EntityManager.AllEntities.GetEntities(Filters.ToArray());
// If the currently stored last result is null, this is the first update.
// This means all entities are to be handled as new.
if (LastResult == null)
{
foreach (var e in result)
{
OnEntityAdded(e);
}
}
else
{
// Determine all entities that got removed
foreach (var e in LastResult.Except(result))
{
OnEntityRemoved(e);
}
// Determine all entites that got added
foreach (var e in result.Except(LastResult))
{
OnEntityAdded(e);
}
}
// Save current result for next update
LastResult = result;
// Call the internal update implementation
base.Update(elapsedTicks);
}
/// <summary> /// Method that implements the actual work the system does. /// </summary> /// <param name="elapsedTicks">The amount of ticks that elapsed since the last update</param> /// <param name="entities">Set of pre-filtered entities that the system can work on</param> protected abstract void Update(long elapsedTicks, EntityQueryResult entities);