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# underlyingErrorsKey

A key whose value is the array of errors that contributed to this error.

```
static let underlyingErrorsKey: CLSErrorUserInfoKey
```

## Discussion

This key only appears for errors with code [`partialFailure`](/documentation/ClassKit/CLSError/partialFailure) in Swift or [`CLSError.Code.partialFailure`](/documentation/ClassKit/CLSError/Code/partialFailure) in Objective-C, signifying that more than one error occurred.

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