Content Primitives

The MGLFeature protocol is used to provide details about geographic features contained in an MGLShapeSource or MGLVectorTileSource object. Each concrete subclass of MGLShape in turn has a subclass that conforms to this protocol. A feature object associates a shape with an optional identifier and attributes.

You can add custom data to display on the map by creating feature objects and adding them to an MGLShapeSource using the -[MGLShapeSource initWithIdentifier:shape:options:] method or MGLShapeSource.shape property.

In addition to adding data to the map, you can also extract data from the map: -[MGLMapView visibleFeaturesAtPoint:] and related methods return feature objects that correspond to features in the source. This enables you to inspect the properties of features in vector tiles loaded by MGLVectorTileSource objects. You also reuse these feature objects as overlay annotations.

While it is possible to add MGLFeature-conforming objects to the map as annotations using -[MGLMapView addAnnotations:] and related methods, doing so has trade-offs:

• Features added as annotations will not have identifier or attributes properties when used with feature querying.

• Features added as annotations become interactive. Taps and selection can be handled in -[MGLMapViewDelegate mapView:didSelectAnnotation:].

An MGLPointFeature object associates a point shape with an optional identifier and attributes.

An MGLPolygonFeature object associates a polygon shape with an optional identifier and attributes.

An MGLPolylineFeature object associates a polyline shape with an optional identifier and attributes.

A polyline feature is known as a LineString feature in GeoJSON.

An MGLMultiPolygonFeature object associates a multipolygon shape with an optional identifier and attributes.

An MGLMultiPolylineFeature object associates a multipolyline shape with an optional identifier and attributes.

A multipolyline feature is known as a MultiLineString feature in GeoJSON.

An MGLPointCollectionFeature object associates a point collection with an optional identifier and attributes.

A point collection feature is known as a MultiPoint feature in GeoJSON.

An MGLShapeCollectionFeature object associates a shape collection with an optional identifier and attributes.

MGLShapeCollectionFeature is most commonly used to add multiple shapes to a single MGLShapeSource. Configure the appearance of an MGLSource’s shape collection collectively using an MGLSymbolStyleLayer object, or use multiple instances of MGLCircleStyleLayer, MGLFillStyleLayer, and MGLLineStyleLayer to configure the appearance of each kind of shape inside the collection.

A shape collection feature is known as a feature collection in GeoJSON.