# Global Events [![](Logo-Tiny.png)](/../../#glossary)
ME.ECS has Global Event files to use events outside the ECS logic step.
To add Global Event object to your project, choose **Create/ME.ECS/Global Event** menu and create your event file.
In GlobalEvent file you can set up `callOthers` array to call other events when this event fired. Note that child events would run before the main event and you should avoid cyclic dependencies manually.

For example if you need to change UI button state when your player's health changes, you can fire the event inside any **AdvanceTick** step like this:
```csharp
void AdvanceTick(float deltaTime) {
  ...
  this.feature.testEvent.Execute();
  ...
}
```

In your feature's inspector you must to set up `testEvent` link to be sure it's not null.
In your UI script you need to set up subscribtion onto your `testEvent`:
```csharp
public GlobalEvent testEvent;
void Start() {
  this.testEvent.Subscribe(this.TestEventCallback);
}

void OnDestroy() {
  this.testEvent.Unsubscribe(this.TestEventCallback);
}

private void TestEventCallback(in Entity entity) {
  // Do some work
}
```

> Note, that Execute method doesn't run immediatelly, so it's wait until ticks job has been ended.

```csharp
GlobalEvent::Execute(); // Make a call with Entity.Empty and GlobalEventType.Visual
GlobalEvent::Execute(in entity); // Make a call with GlobalEventType.Visual
GlobalEvent::Execute(in entity, GlobalEventType.Visual); // Make a call after all ticks work is done
GlobalEvent::Execute(in entity, GlobalEventType.Logic); // Make a call after current tick work is done
```

> To make a call immediatelly you should use **GlobalEvent::Run()** method, but note that it is not recommended.

> Please note, that Execute events works only once by unique GlobalEvent keys. For example: if you call Execute on the same GlobalEvent instance twice with the same entity - only one event would be fired.

You can cancel event don't want to call this event anymore. Note that you need to cancel the same method signature or parameters as the Execute methood.
```csharp
void AdvanceTick(float deltaTime) {
  ...
  this.feature.testEvent.Execute();
  this.feature.testEvent.Cancel(); // Works
  ...
  this.feature.testEvent.Execute(in entity);
  this.feature.testEvent.Cancel(in entity); // Works
  ...
  this.feature.testEvent.Execute(in entity);
  this.feature.testEvent.Cancel(); // Don't work
  ...
}
```
Note that Cancel events will send cancel to all child events too.
All Global Events run once and removed after this call, so you shoudn't Cancel them manually.

[![](Footer.png)](/../../#glossary)