*| [JavaECS](../../README.md) | [docs](../overview.md) | [system](./dir.md) | system[]().md*
# System

### In this section
[About](#About)

[Implementation](#Implementation)

[Examples](#Examples)

[Notes](#Notes)


## About
The system runs operations that must be performed on its assoiciated components.

Typically, this is expected to be run every frame, though this is not a strict requirement.

A system must implement the Runnable interface (this is a limited case of inheritence in this library)

This allows a simpler implementation of any system, and also allows concurrency to be implemented with relative ease.




Examples of the `system` include the `health_system`; which reads the value of the entitie's `health` component and ensures h > 0.
``` java
void health_system(){
    for (i = 0; i < registeredComponents.size(); i++){
        if (registeredComponents[i].health <= 0){
            registeredComponents[i].dead = true;
            if (registeredComponents[i].isPlayer){
                GameOver();
            }
        }
    }
}
```
## Implementation

The systems are managed by the following code:

``` java
class SystemManager{
    ECS baseECS;
    int systemIndex;

    public SystemManager(ECS baseECS){
        this.baseECS = baseECS;
        systemIndex = 0;
    }
}
```

## Examples

## Notes
* Each system is represented by a name-index pair, and the action that gets executed every time the system is performed.    
    * This is implicitly sequential, but a custom system that performs concurrent actions can be implemented.
    * Care must be taken to ensure all threads are synchronised before the concurrent system finishes its execution