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# os_activity_t

An object that represents an activity triggered by the user.

```
typedef NSObject<OS_os_activity> * os_activity_t;
```

## Topics

### Choosing a Special Activity

[`OS_ACTIVITY_NONE`](/documentation/os/OS_ACTIVITY_NONE)

A special value that indicates a nonexistent activity.

[`OS_ACTIVITY_CURRENT`](/documentation/os/OS_ACTIVITY_CURRENT)

A special value that selects the current activity, if there is one.


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