# GeoJSONDelegate A delegate object that controls a GeoJSON import to override default behavior and provide custom style. ``` interface GeoJSONDelegate ``` ## Overview The delegate object provides hooks into the key moments in the GeoJSON import process. When you pass a delegate object to the [`importGeoJSON(data, callback)`](/documentation/MapKitJS/mapkit/importGeoJSON) method, you can: - Modify or replace annotations and overlays before MapKit JS adds them to the [`ItemCollection`](/documentation/MapKitJS/ItemCollection) object. - Override the default GeoJSON mapping behavior. - Provide custom styling by implementing [`styleForOverlay(overlay, geoJSON)`](/documentation/MapKitJS/GeoJSONDelegate/styleForOverlay). - Receive feedback on the result from importing GeoJSON data. ## Topics ### Overriding items [`itemForFeature?( item: Item | null, geoJSON: GeoJSONTypes.Feature, ): Item | null;`](/documentation/MapKitJS/GeoJSONDelegate/itemForFeature) Overrides a feature. [`itemForFeatureCollection?( itemCollection: ItemCollection, geoJSON: D, ): ItemCollection | Item[] | null;`](/documentation/MapKitJS/GeoJSONDelegate/itemForFeatureCollection) Overrides a feature collection. [`itemForLineString?( overlay: PolylineOverlay, geoJSON: GeoJSONTypes.LineString, ): PolylineOverlay | null;`](/documentation/MapKitJS/GeoJSONDelegate/itemForLineString) Overrides a line string. [`itemForMultiLineString?( itemCollection: ItemCollection, geoJSON: D, ): ItemCollection | Item[] | null;`](/documentation/MapKitJS/GeoJSONDelegate/itemForMultiLineString) Overrides a multiline string. [`itemForPoint?( coordinate: Coordinate, geoJSON: GeoJSONTypes.Point, ): Item | null;`](/documentation/MapKitJS/GeoJSONDelegate/itemForPoint) Overrides a point. [`itemForMultiPoint?( itemCollection: ItemCollection, geoJSON: D, ): ItemCollection | Item[] | null;`](/documentation/MapKitJS/GeoJSONDelegate/itemForMultiPoint) Overrides a multipoint object. [`itemForPolygon?( overlay: PolygonOverlay, geoJSON: GeoJSONTypes.Polygon, ): PolygonOverlay | null;`](/documentation/MapKitJS/GeoJSONDelegate/itemForPolygon) Overrides a polygon. [`itemForMultiPolygon?( itemCollection: ItemCollection, geoJSON: D, ): ItemCollection | Item[] | null;`](/documentation/MapKitJS/GeoJSONDelegate/itemForMultiPolygon) Overrides a multipolygon. [`styleForOverlay?( overlay: PolylineOverlay | PolygonOverlay, geoJSON: GeoJSONTypes.LineString | GeoJSONTypes.Polygon, ): Style;`](/documentation/MapKitJS/GeoJSONDelegate/styleForOverlay) Overrides the style of overlays. ### Handling errors and completion [`geoJSONDidComplete?( result: ItemCollection, geoJSON: D, ): void;`](/documentation/MapKitJS/GeoJSONDelegate/geoJSONDidComplete) Completes the GeoJSON import. [`geoJSONDidError?( error: GeoJSONImportError | Error, geoJSON?: GeoJSONTypes.GeoJSON, ): void;`](/documentation/MapKitJS/GeoJSONDelegate/geoJSONDidError) Indicates when the GeoJSON import fails. ### Instance Methods [`itemForGeometryCollection?( item: ItemCollection, object: D, ): ItemCollection | Item[] | null;`](/documentation/MapKitJS/GeoJSONDelegate/itemForGeometryCollection) Overrides a geometry collection with the provided item and object. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)