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# parser(_:resolveExternalEntityName:systemID:)

Sent by a parser object to its delegate when it encounters a given external entity with a specific system ID.

```
optional func parser(_ parser: XMLParser, resolveExternalEntityName name: String, systemID: String?) -> Data?
```

## Parameters

`parser`

A parser object.

`name`

A string that specifies the external name of an entity.

`systemID`

A string that specifies the system ID for the external entity.

## Return Value

An [`NSData`](/documentation/Foundation/NSData) object that contains the resolution of the given external entity.

## Discussion

The delegate can resolve the external entity (for example, locating and reading an externally declared DTD) and provide the result to the parser object as an `NSData` object.

## See Also

[`parser(_:foundExternalEntityDeclarationWithName:publicID:systemID:)`](/documentation/Foundation/XMLParserDelegate/parser(_:foundExternalEntityDeclarationWithName:publicID:systemID:))

Sent by a parser object to its delegate when it encounters an external entity declaration.

[`parser(_:foundUnparsedEntityDeclarationWithName:publicID:systemID:notationName:)`](/documentation/Foundation/XMLParserDelegate/parser(_:foundUnparsedEntityDeclarationWithName:publicID:systemID:notationName:))

Sent by a parser object to its delegate when it encounters an unparsed entity declaration.


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