---
title: error
framework: coredata
role: symbol
role_heading: Type Property
path: coredata/nsmergepolicy/error
---

# error

The default merge policy for all managed object contexts.

## Declaration

```swift
class var error: NSMergePolicy { get }
```

## Discussion

Discussion If a save fails because of conflicting objects, you can find the IDs of those objects in error’s userInfo dictionary. Use the NSInsertedObjectsKey and NSUpdatedObjectsKey keys to extract the object IDs.

## See Also

### Defining Merge Policies

- [mergeByPropertyStoreTrump](coredata/nsmergepolicy/mergebypropertystoretrump.md)
- [mergeByPropertyObjectTrump](coredata/nsmergepolicy/mergebypropertyobjecttrump.md)
- [overwrite](coredata/nsmergepolicy/overwrite.md)
- [rollback](coredata/nsmergepolicy/rollback.md)
- [Merge Policies](coredata/merge-policies.md)