How to add linestring in OpenLayers from GeoJSON property

Question

I have a map with a simple GeoJSON file layer (several towns) which has a 'bbox' property for each town. It is a point or a linestring. The GeoJSON file looks like this:

{"type":"FeatureCollection","features":[{"type":"Feature","properties":{"name":"Rome","bbox":"12.486137, 41.891775, 12.487089, 41.891481"},"geometry":{"type":"Point","coordinates":[12.486137,41.891775]}}]}

Everything is fine when I use the usual way to add a GeoJSON file as Vector Layer. But how can I add a geometry from 'bbox' property of the file as a different layer? Should I add some brackets and commas?

I tried something like this but it didn't add anything:

const styleBBox = new Style({
    fill: new Fill(),
    stroke: new Stroke({
        color: '#000',
        width: 1,
    })
});
const BBox = new VectorLayer({
    source: new VectorSource(),
    style: function (feature) {
        const coordinates = feature.get('bbox');
        styleBBox.getGeometry().getCoordinates(coordinates);
        return styleBBox;
    },
});

Answer 1

You will need to specify geometry in the style if you need to display a different geometry to the feature's own geometry. You can convert a bbox to a polygon geometry using fromExtent https://openlayers.org/en/latest/apidoc/module-ol_geom_Polygon.html#.fromExtent

const BBox = new VectorLayer({
    source: new VectorSource(),
    style: new Style({
      geometry: function(feature) {
        return fromExtent(
          feature.get('bbox').split(',').map(Number)
        ).transform('EPSG:4326', map.getView().getProjection());
      },
      stroke: new Stroke({
        width: 2,
        color: 'black'
      }),
    }),
});

Note that your bbox coordinates are non-standard and may be rejected - they should represent the SW and NE corners https://datatracker.ietf.org/doc/html/rfc7946#section-5