I don't understand the expected specs for GeoJSON data in OpenLayers whether readFeatures() / readFeature() / readGeometry() are used?

Question

I work on a GIS web app using GeoDjango and I struggle reading and displaying a multipoint geometry on my map.

If I serialize my GEOSGeometry object to GeoJSON, I can get the following JSON file :

{ "type": "MultiPoint", "coordinates": [ [ X0, Y0, Z0 ], [ X1, Y1, Z1 ], ... ]}

Now, when I want to read this data using readGeometry() as follows

var vectorSource = new ol.source.Vector({
        features: (new ol.format.GeoJSON()).readGeometry(geojson_object),
    });

I get the error SyntaxError: JSON.parse: expected property name or '}' at line 1 column 3 of the JSON data

I tried parsing my data using GeoJSONLint but it does seem correct.

So I tried to use readFeature() (as I only have one feature) as a matter of testing with slight modification to my geojson file :

{ "type": "Feature", "geometry" : { "type": "MultiPoint", "coordinates": [ [ X0, Y0, Z0 ], [ X1, Y1, Z1 ], ... ] } }

Then I get TypeError: n.features.getArray is not a function

Again, if I use readFeatures() on the same feature object, I get no error whereas it should expect a collection of features, right ?

What am I missing ? The openlayers documentation is not that clear to me.

Answer 1

The feature property in a vector source must be an array of features. Only readFeatures returns an array. Results from the other methods need to be made into an array of features

    features: (new ol.format.GeoJSON()).readFeatures(geojson_object),

    features: [ (new ol.format.GeoJSON()).readFeature(geojson_object) ],

    features: [ new ol.Feature((new ol.format.GeoJSON()).readGeometry(geojson_object)) ],