terriajs/lib/Core/updateFromJson.js

Geospatial data visualization platform.

'use strict';

/*global require*/
var defaultValue = require('terriajs-cesium/Source/Core/defaultValue');
var defined = require('terriajs-cesium/Source/Core/defined');
var when = require('terriajs-cesium/Source/ThirdParty/when');
/**
 * Updates an object from a JSON representation of the object.  Only properties that actually exist on the object are read from the JSON,
 * and the object has the opportunity to inject specialized deserialization logic by providing an `updaters` property.
 * @param {Object} target The object to update from the JSON.
 * @param {Object} json The JSON description.  The JSON should be in the form of an object literal, not a string.
 * @param {Object} [options] Optional parameters to custom updaters.
 * @return {Promise} A promise that resolves when the update completes.
 */
function updateFromJson(target, json, options) {
    options = defaultValue(options, defaultValue.EMPTY_OBJECT);

    var promises = [];

    for (var propertyName in target) {
        if (target.hasOwnProperty(propertyName) && shouldBeUpdated(target, propertyName, json)) {
            if (target.updaters && target.updaters[propertyName]) {
                promises.push(target.updaters[propertyName](target, json, propertyName, options));
            } else {
                target[propertyName] = json[propertyName];
            }
        }
    }

    return when.all(promises);
}

/**
 * Determines whether this property is valid for updating.
 */
function shouldBeUpdated(target, propertyName, json) {
    return (json[propertyName] !== undefined) && // Must have a value to update to
        propertyName.length > 0 && // Must have a name to update
        propertyName[0] !== '_' && // Must not be a private property
        (propertyName !== 'id' || !defined(target.id)); // Must not be overwriting 'id'
}

module.exports = updateFromJson;