geojson as url source + turf.js + manipulation of subset of features' properties

0
votes

mapbox-gl-js version: >=0.27.0 <=0.38.0

(1) I have a Feature geojson type of a single polygon adding to my map from a url source.

(2) I also have a FeatureCollection geojson type of ~4k polygons adding to the map also from a url source.

I use turf.intersect between (1) and (2) to select the intersecting polygons of (2).

I then store the intersecting polygons [a sub-set of (2)] to an array.

I then manipulate the values of some properties of those intersecting polygons with simple math.

I now want to update (2) with the resulting values of the array.

I would love to use something like setData to update (2), but that is not possible for a subset which also is not (a) a geojson data object or (b) a url to one as specified in the docs.

Hopefully I have explained this sufficiently. If so, what is the suggested workflow in this case?

1
mapboxmapbox-gl-jsmapbox-gl
Your data set (2) should, in the end, be an intersection of the original set (2) and the updated subset? – Scarysize
Yes, exactly Scarysize. The updated values of the properties of each object in the subset should replace the original values. – Shawn Goulet

1 Answers

1
votes

Mapbox is not good at sharing if you let it load the GeoJSON; see https://github.com/mapbox/mapbox-gl-js/issues/1762 If you want to manipulate the data yourself, you should load it yourself, then pass it to Mapbox. For example:

// load your data via ajax however you want
const promises = {
  polygon: $.get('.../geojson.json'),
  collection: $.get('.../feature-collection.json'),
};

// setup your map
const map = new mapboxgl.Map({...});
map.on('load', () => {
  RSVP.hash(promises).then((data) => {
    map.addSource('my-data', {
      type: 'geojson',
      // transform does intersection and updates,
      // then outputs a GeoJSON formatted object
      data: transform(data.polygon, data.collection),
    });
  });
});