---
title: toOneRelationshipKeys
framework: foundation
role: symbol
role_heading: Instance Property
path: foundation/nsclassdescription/toonerelationshipkeys
---

# toOneRelationshipKeys

Overridden by subclasses to return the keys for the to-one relationship properties of instances of the described class.

## Declaration

```swift
var toOneRelationshipKeys: [String] { get }
```

## Return Value

Return Value An array of NSString objects containing the names of the to-one relationship properties of instances of the described class.

## Discussion

Discussion To-one relationship properties are single objects. If you have an instance of the class the receiver describes, you can use the NSObject instance method toOneRelationshipKeys instead.

## See Also

### Related Documentation

- [attributeKeys](foundation/nsclassdescription/attributekeys.md)

### Relationship keys

- [inverse(forRelationshipKey:)](foundation/nsclassdescription/inverse(forrelationshipkey:).md)
- [toManyRelationshipKeys](foundation/nsclassdescription/tomanyrelationshipkeys.md)