openlayers/src/ol/Object.js

/**
 * @module ol/Object
 */
import {getUid} from './util.js';
import ObjectEventType from './ObjectEventType.js';
import Observable from './Observable.js';
import Event from './events/Event.js';
import {assign} from './obj.js';


/**
 * @classdesc
 * Events emitted by {@link module:ol/Object~BaseObject} instances are instances of this type.
 */
export class ObjectEvent extends Event {

  /**
   * @param {string} type The event type.
   * @param {string} key The property name.
   * @param {*} oldValue The old value for `key`.
   */
  constructor(type, key, oldValue) {
    super(type);

    /**
     * The name of the property whose value is changing.
     * @type {string}
     * @api
     */
    this.key = key;

    /**
     * The old value. To get the new value use `e.target.get(e.key)` where
     * `e` is the event object.
     * @type {*}
     * @api
     */
    this.oldValue = oldValue;

  }

}


/**
 * @classdesc
 * Abstract base class; normally only used for creating subclasses and not
 * instantiated in apps.
 * Most non-trivial classes inherit from this.
 *
 * This extends {@link module:ol/Observable} with observable
 * properties, where each property is observable as well as the object as a
 * whole.
 *
 * Classes that inherit from this have pre-defined properties, to which you can
 * add your owns. The pre-defined properties are listed in this documentation as
 * 'Observable Properties', and have their own accessors; for example,
 * {@link module:ol/Map~Map} has a `target` property, accessed with
 * `getTarget()` and changed with `setTarget()`. Not all properties are however
 * settable. There are also general-purpose accessors `get()` and `set()`. For
 * example, `get('target')` is equivalent to `getTarget()`.
 *
 * The `set` accessors trigger a change event, and you can monitor this by
 * registering a listener. For example, {@link module:ol/View~View} has a
 * `center` property, so `view.on('change:center', function(evt) {...});` would
 * call the function whenever the value of the center property changes. Within
 * the function, `evt.target` would be the view, so `evt.target.getCenter()`
 * would return the new center.
 *
 * You can add your own observable properties with
 * `object.set('prop', 'value')`, and retrieve that with `object.get('prop')`.
 * You can listen for changes on that property value with
 * `object.on('change:prop', listener)`. You can get a list of all
 * properties with {@link module:ol/Object~BaseObject#getProperties}.
 *
 * Note that the observable properties are separate from standard JS properties.
 * You can, for example, give your map object a title with
 * `map.title='New title'` and with `map.set('title', 'Another title')`. The
 * first will be a `hasOwnProperty`; the second will appear in
 * `getProperties()`. Only the second is observable.
 *
 * Properties can be deleted by using the unset method. E.g.
 * object.unset('foo').
 *
 * @fires ObjectEvent
 * @api
 */
class BaseObject extends Observable {

  /**
   * @param {Object<string, *>=} opt_values An object with key-value pairs.
   */
  constructor(opt_values) {
    super();

    // Call {@link module:ol/util~getUid} to ensure that the order of objects' ids is
    // the same as the order in which they were created.  This also helps to
    // ensure that object properties are always added in the same order, which
    // helps many JavaScript engines generate faster code.
    getUid(this);

    /**
     * @private
     * @type {!Object<string, *>}
     */
    this.values_ = {};

    if (opt_values !== undefined) {
      this.setProperties(opt_values);
    }
  }

  /**
   * Gets a value.
   * @param {string} key Key name.
   * @return {*} Value.
   * @api
   */
  get(key) {
    let value;
    if (this.values_.hasOwnProperty(key)) {
      value = this.values_[key];
    }
    return value;
  }

  /**
   * Get a list of object property names.
   * @return {Array<string>} List of property names.
   * @api
   */
  getKeys() {
    return Object.keys(this.values_);
  }

  /**
   * Get an object of all property names and values.
   * @return {Object<string, *>} Object.
   * @api
   */
  getProperties() {
    return assign({}, this.values_);
  }

  /**
   * @param {string} key Key name.
   * @param {*} oldValue Old value.
   */
  notify(key, oldValue) {
    let eventType;
    eventType = getChangeEventType(key);
    this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
    eventType = ObjectEventType.PROPERTYCHANGE;
    this.dispatchEvent(new ObjectEvent(eventType, key, oldValue));
  }

  /**
   * Sets a value.
   * @param {string} key Key name.
   * @param {*} value Value.
   * @param {boolean=} opt_silent Update without triggering an event.
   * @api
   */
  set(key, value, opt_silent) {
    if (opt_silent) {
      this.values_[key] = value;
    } else {
      const oldValue = this.values_[key];
      this.values_[key] = value;
      if (oldValue !== value) {
        this.notify(key, oldValue);
      }
    }
  }

  /**
   * 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).
   * @param {Object<string, *>} values Values.
   * @param {boolean=} opt_silent Update without triggering an event.
   * @api
   */
  setProperties(values, opt_silent) {
    for (const key in values) {
      this.set(key, values[key], opt_silent);
    }
  }

  /**
   * Unsets a property.
   * @param {string} key Key name.
   * @param {boolean=} opt_silent Unset without triggering an event.
   * @api
   */
  unset(key, opt_silent) {
    if (key in this.values_) {
      const oldValue = this.values_[key];
      delete this.values_[key];
      if (!opt_silent) {
        this.notify(key, oldValue);
      }
    }
  }
}


/**
 * @type {Object<string, string>}
 */
const changeEventTypeCache = {};


/**
 * @param {string} key Key name.
 * @return {string} Change name.
 */
export function getChangeEventType(key) {
  return changeEventTypeCache.hasOwnProperty(key) ?
    changeEventTypeCache[key] :
    (changeEventTypeCache[key] = 'change:' + key);
}


export default BaseObject;