# Class: Snap

This documentation is for OpenLayers v10.9.0. The latest is v.

## ol/interaction/Snap~Snap

    import Snap from 'ol/interaction/Snap.js';

Handles snapping of vector features while modifying or drawing them. The features can come from a `VectorSource` or `Collection` Any interaction object that allows the user to interact with the features using the mouse can benefit from the snapping, as long as it is added before.

The snap interaction modifies map browser event `coordinate` and `pixel` properties to force the snap to occur to any interaction that uses them.

Example:

    import Snap from 'ol/interaction/Snap.js';

    const snap = new Snap({
      source: source
    });

    map.addInteraction(snap);

#### new Snap(options)

interaction/Snap.js, line 320

  Name | Type | Description
  --- | --- | ---
  `features` | Collection<Feature> | undefined | Snap to these features. Either this option or source should be provided.
  `source` | VectorSource | undefined | Snap to features from this source. Either this option or features should be provided
  `edge` | boolean (defaults to true) | Snap to edges.
  `vertex` | boolean (defaults to true) | Snap to vertices.
  `intersection` | boolean (defaults to false) | Snap to intersections between segments.
  `pixelTolerance` | number (defaults to 10) | Pixel tolerance for considering the pointer close enough to a segment or vertex for snapping.
  `segmenters` | Segmenters | undefined | Custom segmenters by `Type`. By default, the following segmenters are used: `Point`: A one-dimensional segment (e.g. `[[10, 20]]`) representing the point. `LineString`: One two-dimensional segment (e.g. `[[10, 20], [30, 40]]`) for each segment of the linestring. `Polygon`: One two-dimensional segment for each segment of the exterior ring and the interior rings. `Circle`: One two-dimensional segment for each segment of a regular polygon with 32 points representing the circle circumference. `GeometryCollection`: All segments of the contained geometries. `MultiPoint`: One one-dimensional segment for each point. `MultiLineString`: One two-dimensional segment for each segment of the linestrings. `MultiPolygon`: One two-dimensional segment for each segment of the polygons.

  ##### Fires:

  - `change` (BaseEvent) - Generic change event. Triggered when the revision counter is increased.
  - `change:active` (ObjectEvent)
  - `error` (BaseEvent) - Generic error event. Triggered when an error occurs.
  - `propertychange` (ObjectEvent) - Triggered when a property is changed.
  - `snap` (SnapEvent) - Triggered upon snapping to vertex or edge
  - `unsnap` (SnapEvent) - Triggered if no longer snapped

### Extends

- PointerInteraction

### Observable Properties

Name | Type | Settable | ObjectEvent type | Description
--- | --- | --- | --- | ---
`active` | boolean | yes | `change:active` | `true` if the interaction is active, `false` otherwise.

### Methods

#### addFeature(feature, register)

interaction/Snap.js, line 446

  Add a feature to the collection of features that we may snap to.

  Name | Type | Description
  --- | --- | ---
  `feature` | Feature | Feature.
  `register` | boolean | undefined | Whether to listen to the feature change or not Defaults to `true`.

#### changed() inherited

Observable.js, line 68

  Increases the revision counter and dispatches a 'change' event.

#### dispatchEvent(event){boolean | undefined} inherited

events/Target.js, line 85

  Dispatches an event and calls all listeners listening for events of this type. The event parameter can either be a string or an Object with a `type` property.

  Name | Type | Description
  --- | --- | ---
  `event` | BaseEvent | string | Event object.

  ##### Returns:

  `false` if anyone called preventDefault on the event object or if any of the listeners returned false.

#### get(key){*} inherited

Object.js, line 136

  Gets a value.

  Name | Type | Description
  --- | --- | ---
  `key` | string | Key name.

  ##### Returns:

  Value.

#### getActive(){boolean} inherited

interaction/Interaction.js, line 82

  Return whether the interaction is currently active.

  ##### Returns:

  `true` if the interaction is active, `false` otherwise.

#### getKeys(){Array.<string>} inherited

Object.js, line 149

  Get a list of object property names.

  ##### Returns:

  List of property names.

#### getMap(){Map | null} inherited

interaction/Interaction.js, line 91

  Get the map associated with this interaction.

  ##### Returns:

  Map.

#### getPointerCount(){number} inherited

interaction/Pointer.js, line 95

  Returns the current number of pointers involved in the interaction, e.g. `2` when two fingers are used.

  ##### Returns:

  The number of pointers.

#### getProperties(){NoInfer.<Properties>} inherited

Object.js, line 158

  Get an object of all property names and values.

  ##### Returns:

  Object.

#### getRevision(){number} inherited

Observable.js, line 79

  Get the version number for this object. Each time the object is modified, its version number will be incremented.

  ##### Returns:

  Revision.

#### handleEvent(evt){boolean}

interaction/Snap.js, line 578

  Name | Type | Description
  --- | --- | ---
  `evt` | MapBrowserEvent | Map browser event.

  ##### Returns:

  `false` to stop event propagation.

#### on(type, listener){EventsKey | Array<EventsKey>} inherited

Observable.js, line 152

  Listen for a certain type of event.

  Name | Type | Description
  --- | --- | ---
  `type` | string | Array.<string> | The event type or array of event types.
  `listener` | function | The listener function.

  ##### Returns:

  Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

#### once(type, listener){EventsKey | Array<EventsKey>} inherited

Observable.js, line 164

  Listen once for a certain type of event.

  Name | Type | Description
  --- | --- | ---
  `type` | string | Array.<string> | The event type or array of event types.
  `listener` | function | The listener function.

  ##### Returns:

  Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

#### removeFeature(feature, unlisten)

interaction/Snap.js, line 666

  Remove a feature from the collection of features that we may snap to.

  Name | Type | Description
  --- | --- | ---
  `feature` | Feature | Feature
  `unlisten` | boolean | undefined | Whether to unlisten to the feature change or not. Defaults to `true`.

#### set(key, value, silent) inherited

Object.js, line 218

  Sets a value.

  Name | Type | Description
  --- | --- | ---
  `key` | string | Key name.
  `value` | * | Value.
  `silent` | boolean | undefined | Update without triggering an event.

#### setActive(active) inherited

interaction/Interaction.js, line 111

  Activate or deactivate the interaction.

  Name | Type | Description
  --- | --- | ---
  `active` | boolean | Active.

#### setProperties(values, silent) inherited

Object.js, line 238

  Sets a collection of key-value pairs. Note that this changes any existing properties and adds new ones (it does not remove any existing properties).

  Name | Type | Description
  --- | --- | ---
  `values` | Partial.<NoInfer.<Properties>> | Values.
  `silent` | boolean | undefined | Update without triggering an event.

#### un(type, listener) inherited

Observable.js, line 173

  Unlisten for a certain type of event.

  Name | Type | Description
  --- | --- | ---
  `type` | string | Array.<string> | The event type or array of event types.
  `listener` | function | The listener function.

#### unset(key, silent) inherited

Object.js, line 262

  Unsets a property.

  Name | Type | Description
  --- | --- | ---
  `key` | string | Key name.
  `silent` | boolean | undefined | Unset without triggering an event.