---
title: "addObserver(toAllBusses:forKeyPath:options:context:)"
framework: audiotoolbox
role: symbol
role_heading: Instance Method
path: "audiotoolbox/auaudiounitbusarray/addobserver(toallbusses:forkeypath:options:context:)"
---

# addObserver(toAllBusses:forKeyPath:options:context:)

Adds a KVO observer for a given property on all busses in the array.

## Declaration

```swift
func addObserver(toAllBusses observer: NSObject, forKeyPath keyPath: String, options: NSKeyValueObservingOptions = [], context: UnsafeMutableRawPointer?)
```

## Parameters

- `observer`: The KVO observer.
- `keyPath`: The property’s key path.
- `options`: The KVO options.
- `context`: The KVO context.

## See Also

### Bus Array Methods and Properties

- [count](audiotoolbox/auaudiounitbusarray/count.md)
- [isCountChangeable](audiotoolbox/auaudiounitbusarray/iscountchangeable.md)
- [ownerAudioUnit](audiotoolbox/auaudiounitbusarray/owneraudiounit.md)
- [busType](audiotoolbox/auaudiounitbusarray/bustype.md)
- [subscript(_:)](audiotoolbox/auaudiounitbusarray/subscript(_:).md)
- [setBusCount(_:)](audiotoolbox/auaudiounitbusarray/setbuscount(_:).md)
- [removeObserver(fromAllBusses:forKeyPath:context:)](audiotoolbox/auaudiounitbusarray/removeobserver(fromallbusses:forkeypath:context:).md)