# `GSFont replaceObjectInFeaturePrefixesAtIndex:withObject:`

*Instance Method*

Replaces the feature prefix at an index.

## Declaration

```swift
func replaceFeaturePrefix(at idx: UInt, with thePrefix: GSFeaturePrefix)
```

```objc
- (void) replaceObjectInFeaturePrefixesAtIndex:(NSUInteger) idx withObject:(GSFeaturePrefix *) thePrefix;
```

```python
replaceObjectInFeaturePrefixesAtIndex_withObject_(idx: int, thePrefix: GSFeaturePrefix)
```

## See Also

### Layout Prefixes

- [`GSFont.featurePrefixes`](/Core/GlyphsCore/GSFont/featurePrefixes) — Feature prefixes in the font.
- [`GSFont countOfFeaturePrefixes`](/Core/GlyphsCore/GSFont/countOfFeaturePrefixes) — The number of feature prefixes.
- [`GSFont objectInFeaturePrefixesAtIndex:`](/Core/GlyphsCore/GSFont/objectInFeaturePrefixesAtIndex:) — The feature prefix at an index.
- [`GSFont featurePrefixForTag:`](/Core/GlyphsCore/GSFont/featurePrefixForTag:) — The feature prefix with the specified name.
- [`GSFont addFeaturePrefix:`](/Core/GlyphsCore/GSFont/addFeaturePrefix:) — Adds a feature prefix.
- [`GSFont insertObject:inFeaturePrefixesAtIndex:`](/Core/GlyphsCore/GSFont/insertObject:inFeaturePrefixesAtIndex:) — Inserts a feature prefix at an index.
- [`GSFont removeFeaturePrefix:`](/Core/GlyphsCore/GSFont/removeFeaturePrefix:) — Removes a feature prefix.
- [`GSFont removeObjectFromFeaturePrefixesAtIndex:`](/Core/GlyphsCore/GSFont/removeObjectFromFeaturePrefixesAtIndex:) — Removes the feature prefix at an index.