openlayers/src/ol/Object.js

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

/**
 * @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 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 ol.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 ol.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 ol.Object#getProperties object.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').
 *
 * @constructor
 * @extends {ol.Observable}
 * @param {Object.<string, *>=} opt_values An object with key-value pairs.
 * @fires ol.Object.Event
 * @api
 */
const BaseObject = function(opt_values) {
  Observable.call(this);

  // Call ol.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);
  }
};

inherits(BaseObject, Observable);


/**
 * @private
 * @type {Object.<string, string>}
 */
BaseObject.changeEventTypeCache_ = {};


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


/**
 * Gets a value.
 * @param {string} key Key name.
 * @return {*} Value.
 * @api
 */
BaseObject.prototype.get = function(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
 */
BaseObject.prototype.getKeys = function() {
  return Object.keys(this.values_);
};


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


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


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


/**
 * @classdesc
 * Events emitted by {@link ol.Object} instances are instances of this type.
 *
 * @param {string} type The event type.
 * @param {string} key The property name.
 * @param {*} oldValue The old value for `key`.
 * @extends {ol.events.Event}
 * @implements {oli.Object.Event}
 * @constructor
 */
BaseObject.Event = function(type, key, oldValue) {
  Event.call(this, 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;

};
inherits(BaseObject.Event, Event);
export default BaseObject;