QueryEngine Object

The QueryEngine object provides an entry point for interacting with spatial data.

Unlike the Map Object, it does not perform any graphic functions.

Rather it allows the user to fetch data, manipulate and filter that data and then decide where that data can be used.

The object is instantiated in the following way:

new Mapzania.QueryEngine()

Parameters

No parameters

Example

 var qry = new Mapzania.QueryEngine();

Methods

usingFeatureCollection

Gets a Query Object based on a A GeoJSON FeatureCollection provided by the user.

This object is a fluent object and can be used to chain method calls to the query as per the example below.

Parameters

Example

var gjson = {
    type: "FeatureCollection",
    features: [...]
};

 var qry = new Mapzania.QueryEngine();

qry.usingFeatureCollection(gjson)
    .filterByText("Landlocked=='Y'")
    .bufferGeometry(500)
    .apply()
    .then(function (data) {
        console.log(data);
    })

usingLayerSource

Gets a Query Object based on the key of the layer-source.

This object is a fluent object and can be used to chain method calls to the query as per the example below.

Parameters

Example

 var qry = new Mapzania.QueryEngine();

    qry.usingLayerSource("COUNTRIES")
        .filterByText("Landlocked=='Y'")
        .bufferGeometry(500)
        .apply()
        .then(function (data) {
            console.log(data);
        })

usingMapLayer

Gets a Query Object based on a layer of an existing Map Object.

It is used specifically to run queries based on the layers of an existing Map Object without interfering with the map itself.

This object is a fluent object and can be used to chain method calls to the query as per the example below.

Parameters

Options

Example

var map = new Mapzania.Map("map-div", "LONDON", function () {

    var qry = new Mapzania.QueryEngine();

    qry.usingMapLayer(map, "WARD", { 
            useState: false, 
            useFilters: true 
        })
        .convertToCentroids()
        .apply()
        .then(function (data) {
            console.log(data);
        });
});