---
title: "data(using:allowLossyConversion:)"
framework: foundation
role: symbol
role_heading: Instance Method
path: "foundation/nsstring/data(using:allowlossyconversion:)"
---

# data(using:allowLossyConversion:)

Returns an NSData object containing a representation of the receiver encoded using a given encoding.

## Declaration

```swift
func data(using encoding: UInt, allowLossyConversion lossy: Bool) -> Data?
```

## Parameters

- `encoding`: A string encoding. For possible values, see doc://com.apple.foundation/documentation/Foundation/NSStringEncoding.
- `lossy`: If doc://com.apple.documentation/documentation/Swift/true, then allows characters to be removed or altered in conversion.

## Return Value

Return Value An NSData object containing a representation of the receiver encoded using encoding. Returns nil if flag is false and the receiver can’t be converted without losing some information (such as accents or case).

## Discussion

Discussion If flag is true and the receiver can’t be converted without losing some information, some characters may be removed or altered in conversion. For example, in converting a character from NSUnicodeStringEncoding to NSASCIIStringEncoding, the character ‘Á’ becomes ‘A’, losing the accent. This method creates an external representation (with a byte order marker, if necessary, to indicate endianness) to ensure that the resulting NSData object can be written out to a file safely. The result of this method, when lossless conversion is made, is the default “plain text” format for encoding and is the recommended way to save or transmit a string object.

## See Also

### Working with Encodings

- [availableStringEncodings](foundation/nsstring/availablestringencodings.md)
- [defaultCStringEncoding](foundation/nsstring/defaultcstringencoding.md)
- [stringEncoding(for:encodingOptions:convertedString:usedLossyConversion:)](foundation/nsstring/stringencoding(for:encodingoptions:convertedstring:usedlossyconversion:).md)
- [localizedName(of:)](foundation/nsstring/localizedname(of:).md)
- [canBeConverted(to:)](foundation/nsstring/canbeconverted(to:).md)
- [data(using:)](foundation/nsstring/data(using:).md)
- [description](foundation/nsstring/description.md)
- [fastestEncoding](foundation/nsstring/fastestencoding.md)
- [smallestEncoding](foundation/nsstring/smallestencoding.md)
- [StringEncodingDetectionOptionsKey](foundation/stringencodingdetectionoptionskey.md)
- [NSString Handling Exception Names](foundation/nsstring-handling-exception-names.md)