---
title: "classes(for:argumentIndex:ofReply:)"
framework: foundation
role: symbol
role_heading: Instance Method
path: "foundation/nsxpcinterface/classes(for:argumentindex:ofreply:)"
---

# classes(for:argumentIndex:ofReply:)

Returns the current list of allowed classes that can appear within the specified collection object argument to the specified method.

## Declaration

```swift
func classes(for sel: Selector, argumentIndex arg: Int, ofReply: Bool) -> Set<AnyHashable>
```

## Parameters

- `sel`: Specifies which method in the protocol you want information about.
- `arg`: Specifies the position (starting at index 0) of the parameter for which you want to obtain the current set of allowed classes. This may be either the position of a parameter in the method itself or the position in its reply block.
- `ofReply`: Pass doc://com.apple.documentation/documentation/Swift/true if arg is an index into the parameters of the reply block, or doc://com.apple.documentation/documentation/Swift/false if it is an index into the parameters of the method itself.

## Discussion

Discussion See setClasses(_:for:argumentIndex:ofReply:) for more explanation.

## See Also

### Related Documentation

- [Daemons and Services Programming Guide](apple-archive/documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/Introduction.html.md)