# Layers and sources

# Adding layers

Geographic features on the map draws as layers. Layer use source object that contains data for layer (for example, GeoJSON object). Source must be added to map and several layers can use common source and draw it's data differently. Also, layer has own configuration object that declares how layer draws on the map. You can read more about it in Mapbox GL JS docs for sources (opens new window) and layers (opens new window).

v-mapbox exposes layers as Vue components. source and layer configuration object passed to layer component as props. There is several layers types for drawing different types of sources. For example adding a layer with GeoJSON data:

<template>
  <MglMap :accessToken="accessToken" :mapStyle.sync="mapStyle">
    <!-- Adding navigation control -->
    <MglNavigationControl position="top-right" />
    <!-- Adding GeoJSON layer -->
    <MglGeojsonLayer
      :sourceId="geoJsonSource.id"
      :source="geoJsonSource"
      layerId="myLayer"
      :layer="geoJsonlayer"
    />
  </MglMap>
</template>

<script>
import { MglMap, MglNavigationControl, MglGeojsonLayer } from "v-mapbox";

export default {
  components: {
    MglMap,
    MglNavigationControl,
    MglGeojsonLayer
  },
  data() {
    return {
      accessToken: "some_token",
      mapStyle: "style_object",
      geoJsonSource: {
        //...some GeoJSON object
      },
      geoJsonLayer: {
        //...some GeoJSON layer configuration object
      }
    };
  }
};
</script>

In this example geoJsonSource can be an object, representing GeoJSON feature or string with URL to GeoJSON.

Sources are stored in Mapbox GL JS Map object by sourceId. If you sure that source already added to map, you can skip source prop and just pass sourceId and use same source for different layers. If you try to add same source with same id twice, VueMapbox would just use source that already existed on the map, but you can set replaceSource prop to true to just replace old source with new one passed in source prop.

By default when Layer components destroying, it removes source from map. If you want to keep source on Map (for example, for future using or if other layers use this source), set clearSource prop to false.

# Reactivity

Layer components watch for changes in object in their layer prop and translate changes to map accordingly. For example, if you change content of filter prop in GeojsonLayer, changes will be automatically applied to layer on the map. Not all layer settings can be set dynamically, currently reactive properties are minzoom, maxzoom, paint, layout and filter.

# Layer getters

GeoJSON and Vector layers has getters for their features: .getRenderedFeatures(filter?), .getSourceFeatures(geometry?, filter?) and .getFeatureState(featureId). They works similar to .queryRenderedFeatures() (opens new window) and .querySourceFeatures() (opens new window) Map methods, but returns features only from source of current layer.

# Layer methods

Layer components has methods move() and remove(). First moves a layer to a different z-position. Second destroys component and removes layer and source from map event if layer created with prop clearSource: false.

# Layer events

Layers emits events when loading data or on user interaction like click. See full list of events in API section

# Migration from 0.1

In versoin 0.1 layer and source options was exposed via separate props. Since 0.2 there are consolidated source object props for data source and layer for layer options. See sources (opens new window) and layers (opens new window) in Mapbox GL JS docs.