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# CFRunLoopTimerCallBack

Callback invoked when a CFRunLoopTimer object fires.

```
typealias CFRunLoopTimerCallBack = (CFRunLoopTimer?, UnsafeMutableRawPointer?) -> Void
```

## Parameters

`timer`

The run loop timer that is firing.

`info`

The `info` member of the [`CFRunLoopTimerContext`](/documentation/CoreFoundation/CFRunLoopTimerContext) structure that was used when creating the run loop timer.

## Discussion

If `timer` repeats, the run loop automatically schedules the next firing time after calling this function, unless you manually update the firing time within this callback by calling [`CFRunLoopTimerSetNextFireDate(_:_:)`](/documentation/CoreFoundation/CFRunLoopTimerSetNextFireDate(_:_:)). If `timer` does not repeat, the run loop invalidates `timer`.

You specify this callback when you create the timer with [`CFRunLoopTimerCreate(_:_:_:_:_:_:_:)`](/documentation/CoreFoundation/CFRunLoopTimerCreate(_:_:_:_:_:_:_:)).

---

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