# `GSFilterHandler`

*Class*

## Declaration

```swift
class GSFilterHandler
```

```objc
@interface GSFilterHandler : NSObject
```

```python
class GSFilterHandler(NSObject)
```

## Topics

### Type Properties

- [`GSFilterHandler.filterInstances`](/Core/GlyphsCore/GSFilterHandler/filterInstances)

### Type Methods

- [`GSFilterHandler activeLayerCallbacks`](/Core/GlyphsCore/GSFilterHandler/activeLayerCallbacks) — all active callbacks
- [`GSFilterHandler addFeatureCodeGenerator:`](/Core/GlyphsCore/GSFilterHandler/addFeatureCodeGenerator:)
- [`GSFilterHandler addFilterClass:`](/Core/GlyphsCore/GSFilterHandler/addFilterClass:)
- [`GSFilterHandler addLayerCallback:forOperation:`](/Core/GlyphsCore/GSFilterHandler/addLayerCallback:forOperation:)
- [`GSFilterHandler applyFilter:withKey:error:font:match:callback:`](/Core/GlyphsCore/GSFilterHandler/applyFilter:withKey:error:font:match:callback:)
- [`GSFilterHandler applyLayerCallbacks:toLayer:error:`](/Core/GlyphsCore/GSFilterHandler/applyLayerCallbacks:toLayer:error:)
- [`GSFilterHandler featureCodeGenerators`](/Core/GlyphsCore/GSFilterHandler/featureCodeGenerators)
- [`GSFilterHandler layerCallbacksForType:`](/Core/GlyphsCore/GSFilterHandler/layerCallbacksForType:) — the callbacks for a certain callbackType
- [`GSFilterHandler removeLayerCallback:forOperation:`](/Core/GlyphsCore/GSFilterHandler/removeLayerCallback:forOperation:)
- [`GSFilterHandler respondToException:`](/Core/GlyphsCore/GSFilterHandler/respondToException:)

## Relationships

### Inherits From

- `NSObject`