Question

I am trying to fill a Dictionary (JavaScript object) and retrieve values (custom objects/classes) from it using a string index. Then once I get the value from the dictionary, I need to invoke a method on this object. Unfortunately, that does not work because once it is being retrieved from the Dictionary, it is just a simple object (typeof returns “object”).

So the thing I’m trying to do is to cast to the object type that was initially pushed into the dictionary, which is in my case: google.visualization.Gauge. (Reference)

I tried to use Object.create but that did not work for me. Below is my code:

var _gauges = {};

var methods = {
    init: function (options) {

        var containers = this;

        if (containers != null && containers != undefined && containers.length > 0) {
            containers.each(function (index, elem) {

                var id = $(elem).attr('id');
                var name = $(elem).data('name');
                var value = $(elem).data('value');

                var data = google.visualization.arrayToDataTable([
            ['Label', 'Value'],
            [name, value]
                ]);

                var options = {
                    width: 400, height: 120,
                    redFrom: 90, redTo: 100,
                    yellowFrom: 75, yellowTo: 90,
                    minorTicks: 5
                };
                var cont = document.getElementById(id);
                var chart = new google.visualization.Gauge(cont);
                _gauges[name] = chart;
                chart.draw(data, options);
            });
        }

    },
    setValue: function (gaugeName, newValue) {
        var thisGauge = _gauges[gaugeName];
        if (thisGauge) {
            thisGauge.setCell(0, 1, newValue);
            //var tmp = Object.create(google.visualization.Gauge, thisGauge);
            //tmp.setCell(0, 1, newValue);
        }
    }

Answer 1

Well, two things:

1. If one of those “Gauge” objects is really getting put into the array correctly, when you get it back out it will emerge unscathed and you can just use it directly; no “casting” necessary.
2. According to the documentation you linked, there is no “setCell” method 🙂