= EntitySets
:revnumber: 2.0
:revdate: 2020/07/27



== Introduction

One difference between Zay-ES and other Entity Systems is that you are allowed to access the system from various threads. This can give your game a huge performance boost because costly tasks can easily be separated out into their own thread.
This leads to a unique design of the components and the introduction to Entity Sets.


== Why EntitySets?

One huge benefit of Zay-ES is that you are able to create a separate class for each job.
This leads to clean code and you always know which class is responsible for bugs.
For example you can have a class for Collision, Movement, Enemies, PlayerInput,….
All of these classes are only interested in entities which have special components.


== How to use them


=== Create an EntitySet

[source,java]
----
//This set is interested in entities with a TestComponent
EntitySet entitySet = entityData.getEntities(TestComponent.class);
----


=== Update an EntitySet

[source,java]
----
 //Apply all new changes to the EntitySet and return false if nothing changed
if(entitySet.applyChanges())
{
    entitySet.getAddedEntities();
    entitySet.getChangedEntities();
    entitySet.getRemovedEntities();
}
----