# PhysicsCallbacks.IContactCallback

> An interface that when implemented, can be called as a target by PhysicsWorld.SendContactCallbacks.

## Definition

* **Type:** Interface
* **Namespace:** [Unity.U2D.Physics](/engine/6000.5/script-reference/unity/u2d/physics.md)
* **Assembly:** UnityEngine.PhysicsCore2DModule

```csharp
public interface PhysicsCallbacks.IContactCallback
```

## Methods

| Method                                                                                                                      | Description                                                                                                                                                                                                                                   |
| --------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [OnContactBegin2D](/engine/6000.5/script-reference/unity/u2d/physics/physicscallbacks/icontactcallback/oncontactbegin2d.md) | Called when a [PhysicsEvents.ContactBeginEvent](/engine/6000.5/script-reference/unity/u2d/physics/physicsevents/contactbeginevent.md) for the object occurs. This will always be called on the main-thread after the simulation has finished. |
| [OnContactEnd2D](/engine/6000.5/script-reference/unity/u2d/physics/physicscallbacks/icontactcallback/oncontactend2d.md)     | Called when a [PhysicsEvents.ContactEndEvent](/engine/6000.5/script-reference/unity/u2d/physics/physicsevents/contactendevent.md) for the object occurs. This will always be called on the main-thread after the simulation has finished.     |