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# CFRunLoopContainsObserver(_:_:_:)

Returns a Boolean value that indicates whether a run loop mode contains a particular CFRunLoopObserver object.

```
func CFRunLoopContainsObserver(_ rl: CFRunLoop!, _ observer: CFRunLoopObserver!, _ mode: CFRunLoopMode!) -> Bool
```

## Parameters

`rl`

The run loop to examine.

`observer`

The run loop observer for which to search.

`mode`

The run loop mode in which to search for `observer`. Use the constant [`commonModes`](/documentation/CoreFoundation/CFRunLoopMode/commonModes) to search for `observer` in the set of objects monitored by all the common modes.

## Return Value

`true` if `observer` is in mode `mode` of the run loop `rl`, otherwise `false`.

## Discussion

If `observer` was added to [`commonModes`](/documentation/CoreFoundation/CFRunLoopMode/commonModes), this function returns `true` if `mode` is either [`commonModes`](/documentation/CoreFoundation/CFRunLoopMode/commonModes) or any of the modes that has been added to the set of common modes.

---

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