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# NSFontDescriptor.FeatureKey

Constants to use as keys to retrieve information about a font descriptor from its feature dictionary.

```
struct FeatureKey
```

## Discussion

These keys are used with [`featureSettings`](/documentation/AppKit/NSFontDescriptor/AttributeName/featureSettings).

## Topics

### Feature Keys

[`typeIdentifier`](/documentation/AppKit/NSFontDescriptor/FeatureKey/typeIdentifier)

A key that indicates the type of the font feature.

[`selectorIdentifier`](/documentation/AppKit/NSFontDescriptor/FeatureKey/selectorIdentifier)

A key that indicates the selector of the font feature.

### Initializers

[`init(_:)`](/documentation/AppKit/NSFontDescriptor/FeatureKey/init(_:))

[`init(rawValue:)`](/documentation/AppKit/NSFontDescriptor/FeatureKey/init(rawValue:))


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