[GIS] Selecting Feature by attribute OpenLayers

kmlopenlayers

I'm attempting to limit the features on a vector layer by searching by some attribute (preferably name). I've managed to get the array of features but cannot seem to work out how to iterate over them until I find one with a specified name.

I saw in earlier versions of OpenLayers there were functions like getFeatureByAttribute which could help but there doesn't seem to be anything like this any more.

Best Answer

If you're using a vector layer with a vector source, getting a specific feature by any of its attributes is easy.

var vectorSource = vectorLayer.getSource();
var features = vectorSource.getFeatures();
var value = 'foo';
var property = 'name';
var found;
for (var i = 0, ii = features.length; i < ii; i++) {
  if (features[i].get(property) === value) {
    found = features[i];
    break;
  }
}
console.log(found);

Feel free, as part of your projet, to create your own util method to accomplish this.

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[GIS] Simplify Multigeometry polygons in QGIS

You will get the same error if you have not selected the feature in the GUI and then select the layer but hit use only selected features.

Also you can try using "vector"->"geometry tools"-> "Multiparts to single parts" This might be installed by fTools, both my installations mac and windows included this tools.

The last merge I did I used the dissolve function in the same "geometry tools" section, rather than merge selected features.

The attribute view gives a good overview of the number of features, but not feature parts.

For feature counts there is processing tool box-> SAGA-> shapes - polygons -> polygon properties and polygons parts to seperate polygon

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It's been a while but I stumbled upon the same problem. Your code helped me a lot, this is the solution I came up with (not that I'm using typescript, to convert it to JS remove the types after the variables):

Here is my code:

// create the select interaction
var select = new ol.interaction.Select({
    style: styleClick,
    condition: function (mapBrowserEvent) {
        // check if it is a click event
        if (!ol.events.condition.singleClick(mapBrowserEvent))
            return false;

        // collect all the features at the click event
        var features = [];
        self.map.forEachFeatureAtPixel(mapBrowserEvent.pixel, function (feature_, layer) {
            var features_ = feature_.get('features');
            // get all the features in that place
            for (let i = 0; i < features_.length; i++)
                features.push(features_[i]);
        });
        // check if one or more featres on this place (a cluster always contains multiple features!)
        if (features !== null && features.length > 1) {
            return false;
        } else if (features.length === 1) {
            // trigger the callback for the selected feature (best place I found, since the  ol.interaction.Select doesn't seem to have a change event)
            // YOURCALLBACK FKT (e.g. callback(features[0])
            return true;
        }

        // default exit rout
        return false;
    }
});
this.map.addInteraction(select);

Best Answer

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[GIS] Simplify Multigeometry polygons in QGIS

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