I don’t really have the time to do a proper Intro to Backbone post but fortunately many others have done so. Some are better than others though, so what I thought I’d do is share some of the resources I found most helpful and mention a few of the additional libraries we’re using.

It’s true that the learning curve is somewhat steep but once you dive in, it’s not really that bad. A good place to start is http://backbonetutorials.com/ which provides a brief introduction to the various backbone components. A very easy to understand and quite good hello world example is at http://arturadib.com/hello-backbonejs/docs/1.html. This one is cool because it starts very simply and progressively adds complexity.

Rob Conery wrote a two part post discussing some of the problems he saw with many Backbone tutorials. I was really happy to see this because I shared some of his objections.

One of the things I missed when I first started this project was model binding. Then I found this awesome plugin for Backbone which provides two-way, convention-based model binding. This was ridiculously easy to use and it allowed me to slim down my views considerably.

One issue I had was that the particular needs of our app called for messaging between various components other than just a model and its view. For instance, I needed my Results view to know when my Criteria model changed so it could update itself with new data based on the Criteria model that changed; but other than that, the Results view needed no knowledge of the Criteria model. I initially used a shared reference to the Criteria model but I didn’t love it because I wanted my components to be more loosely coupled. I now think that would have been fine but my dissatisfaction lead me to this post that suggests using the Event Aggregator pattern. It’s really very simple. Since I already had all my modules namespaced, I just put my event aggregator as a property on my namespace object and all my other modules have access to it:

dts.eventAggregator = _.extend({}, Backbone.Events);

Then you can just do

dts.eventAggregator.bind('fooEvent', fooEventHandler, this);

and

dts.eventAggregator.trigger('fooEvent', {/*event arguments*/});

I found this very good post discussing a good approach to avoiding memory leaks. One of the comments lead me to this StackOverflow post discussing the same issue. I think a combination of these two approaches would work well.

Though I’m new to javascript mvc frameworks, I’ve been using javascript templating for a while now. I’ve mostly been using jQuery Templates which I like just fine, but I took this opportunity to try some other templating engines. I ended up settling on icanhaz.js because it uses the mustache.js template syntax (it actually uses mustache under the covers, I think) which I like very much and because it precompiles the templates into functions (thus improving performance, I assume) and hangs them right on the ich object with the function name corresponding to the id of the template (thus making it very easy to use). I’ll definitely be sticking with icanhaz going forward.

Of course, one of the best things about the MVC pattern is that it lends itself quite well to testing. I found a very nice multi-part post on testing backbone applications – the first part is here. I had used qUnit before so I decided to stay with it to minimize the risk of my head exploding from all the new stuff (though I was tempted to give Jasmine a whirl). The post above lead me to sinon.js (and its qUnit adapter, sinon-qunit) which is a really great little library that provides test spies, stubs, and mocks. Unit testing this stuff was fun and it actually helped me uncover some bugs that I didn’t notice in my ui testing.

I’ve learned a ton this week, which is always fun, and I’m looking forward to building more applications with Backbone.js.

I also borrowed and modified some code from John Resig to format the dates. Oh yeah, it also depends on the jQuery Templating Plugin.

It takes an options argument with a required url property and a couple of other optional properties, gets the feed, and loads the items into semantic markup inside the selected element. You can then style it any way you want.

/**
*  Plugin which uses the Google AJAX Feed API for creating feed content
*  depends on jquery template plugin
*  very loosely based on http://jquery.malsup.com/gfeed/
*/

(function ($) {
    if (!$.template) {
        alert('You must include the jQuery Templating Plugin script');
        return;
    }

    //feed item template
    var templateHtml = '<div>' +
                            '<div class="feed-item">' +
                                '<a href="${link}" target="_blank">' +
                                    '<h2 class="feed-title">${title}</h2>' +
                                '</a>' +
                                '<div class="feed-snippet">${contentSnippet}</div>' +
                                '<div class="feed-footer">Posted ${publishedDate} by ${author}</div>' +
                            '</div>' +
                        '</div>';

    //from based on code from John Resig
    // - http://ejohn.org/blog/javascript-pretty-date/
    function prettyDate(dateString) {
        var date = new Date(dateString);
        diff = (((new Date()).getTime() - date.getTime()) / 1000),
		            day_diff = Math.floor(diff / 86400);

        if (isNaN(day_diff) || day_diff < 0) {
            return;
        }

        return day_diff == 0 && (
			        diff < 60 && "just now" ||
			        diff < 120 && "1 minute ago" ||
			        diff < 3600 && Math.floor(diff / 60) + " minutes ago" ||
			        diff < 7200 && "1 hour ago" ||
			        diff < 86400 && Math.floor(diff / 3600) + " hours ago") ||
		            day_diff == 1 && "Yesterday" ||
		            day_diff < 7 && day_diff + " days ago" ||
		            day_diff < 42 && Math.ceil(day_diff / 7) + " weeks ago" ||
                    day_diff >= 42 && Math.floor(day_diff / 31) + " months ago";
    }
    new Date().tou
    $.fn.feed = function (options) {
        var opts = $.extend({
            url: '',
            target: this,
            title: 'The latest from our blog',
            max: 5   // max number of items
        }, options || {});

        //show a loading indicator
        opts.target.append('<div id="feed-loading">loading blog feed...</div>');

        //get the feed items
        var feedItemTemplate = $(templateHtml).template();
        var gFeedsUrl = 'http://ajax.googleapis.com/ajax/services/feed/load?v=1.0&callback=?&num=' + opts.max + '&q='
        $.ajax({
            url: gFeedsUrl + encodeURIComponent(opts.url),
            dataType: 'json',
            success: function (response) {
                //remove the loading indicator
                $('#feed-loading').remove();

                if (response && response.responseData
                                  && response.responseData.feed
                                  && response.responseData.feed.entries) {
                    var feedItems = response.responseData.feed.entries;
                    //map them to format the date
                    $.map(feedItems, function (item, idx) {
                        item.publishedDate = prettyDate(item.publishedDate);
                        return item;
                    });
                    //load the feeds into the dom
                    opts.target.append('<h1>' + opts.title + '</h1><div id="rss-feed"></div>')
                        .find('#rss-feed')
                        .append($.tmpl(feedItemTemplate, feedItems));
                } else {
                    opts.target.append('<div id="feed-error">Unable to retrieve blog feed.</div>');
                }
            }
        });

        return this;
    };
})(jQuery);

Javascript:

obj.date = new Date().toUTCString();

C#:

DateTime date= DateTime.ParseExact(obj.date,
                                  "ddd, MMM d yyyy HH:mm:ss GMT",
                                  CultureInfo.InvariantCulture);

In January of 2007 we bought our house from Jamestown Builders. When it was about a month out of warranty, we noticed that like some of our neighbors’, our driveway had begun to spall.

I called them to see what they were going to do about it and their response was basically that I shouldn’t have parked my car on it in the winter. Well, I didn’t very often, but IT’S A DRIVEWAY! Can I cook in my kitchen? Can I poop in my bathroom? The rationale is that the freeze/ thaw cycles are exacerbated by the stuff they put on the roads (and then drips off my car) to melt ice and that cracks the driveway. According to my research, while that certainly can happen, it should not happen to properly formulated and installed concrete.

Furthermore, I had a concrete driveway in MINNESOTA that was who knows how many years old when I bought the house and on which I parked my truck every day for the 6 years I lived there. Last time I looked (in 2010) that driveway was fine. By now, The Jamestown driveway is 4 years old and it is quite simply disintegrating. I think it’s outrageous that I’m going to have to spend at least $3000 on my driveway when the house is barely 5 years old.

The bottom line is that they clearly had a quality problem with their concrete contractor. They know this perfectly well and if they’d just say so but say, “sorry you’re warranty expired”, I could accept that. But it rankles that they claim it’s my fault and that it’s to be expected for a driveway to disintegrate if you use it for it’s intended purpose.

So I do not recommend purchasing a house from Jamestown Builders.

After a little digging, I found that Mobile Safari doesn’t support single finger scrolling on divs. You have to use two fingers. This is actually documented in the iPad User Guide. Presumably this is because on touch based devices it’s hard to know if you intend to scroll the whole page or just the div. But, like I said, it works perfectly on my Xoom. Now, if I didn’t know this, I certainly can’t expect my users to.

I found that Nick Larson had created a very simple fix to implement single finger scrolling. I took it and rolled it into a jQuery plugin (my first, actually) using Mike Alsup’s plugin pattern. There are other solutions out there but mine has the virtue of being very easy to understand and very light (644 bytes minified).

/*mjuniper 06/21/2011
    based on code from:

http://www.flexmls.com/developers/2011/04/13/

ipad-and-single-finger-scrolling-in-flexmls/
    and http://www.learningjquery.com/2007/10/a-plugin-development-pattern
*/
//
// create closure
//
(function ($) {
    //
    // plugin definition
    //
    $.fn.mobileScroll = function (options) {
        //only do it for iOS devices
        var userAgent = window.navigator.userAgent.toLowerCase();
        if (userAgent.indexOf('ipad') > -1 ||
                userAgent.indexOf('iphone') > -1) {
            this.bind('touchstart', function (evt) {
                var e = evt.originalEvent;
                startY = e.touches[0].pageY;
                startX = e.touches[0].pageX;
            });

            this.bind('touchmove', function (evt) {
                //need the touches property of the native dom event
                // - jquery exposes originalEvent for that
                var e = evt.originalEvent;
                var touches = e.touches[0];
                //cache $(this)
                var $this = $(this);

                // override the touch event’s normal functionality
                e.preventDefault();

                // y-axis
                var touchMovedY = startY - touches.pageY;
                startY = touches.pageY; // reset startY for the next call
                $this.scrollTop($this.scrollTop() + touchMovedY);

                // x-axis
                var touchMovedX = startX - touches.pageX;
                startX = touches.pageX; // reset startX for the next call
                $this.scrollLeft($this.scrollLeft() + touchMovedX);
            });
        }

        return this;
    };
    //
    // end of closure
    //
})(jQuery);

getUcSessions: function (sessionsJsonPath) {
       //if we've got it in localStorage, return that
       var data = localStorage.getItem(_sessionKey);
       if (data) {
           console.debug('got sessions from localStorage.');
           _ucSessions =JSON.parse(data);
           return _ucSessions;
       }

       //otherwise, load the json and stuff it into localstorage
       //here we return a promise that will be resolved when we've gotten and processed all the data
       var dfd = new $.Deferred();
       $.getJson(sessionsJsonPath, function (sessions) {
            _ucSessions = sessions;
            console.debug('got sessions via XHR.');

            dfd.resolve(_ucSessions);
       });
       return dfd.promise();
}

Then to call it, you just do:

$.when(_repo.getUcSessions(args.sessionDataUrl)).then(function (ucSessions) {
    //Do stuff with the sessions...

});

This worked fine on the iPad except that the keypad didn’t collapse. Of course, you can’t directly control the keypad in Javascript but I had a hunch that if I just removed focus from the search field, it would collapse. And it worked! Code (jQuery) below:

$(this).blur();

First off, I used -webkit-user-select:none; to prevent selection of various elements in the ui. This worked flawlessly in Mobile Safari on the iPad but Chrome on Android does not seem to respect it at all.

I also ran into a couple of issues using the ArcGIS Javascript API on the Xoom. Since Android doesn’t support SVG, the JSAPI uses canvas and there are evidently some small problems with their canvas implementation. TextSymbol doesn’t work and neither do any of the fill styles for simple fill symbol except solid and null. Overall the JSAPI works great on the Xoom, though.

I’m told that the text symbol issue will probably be fixed in the 2.3 release.

Blueprint is a css framework I sometimes use. It’s easy to understand and use. But I’ve noticed that it stomps on some ArcGIS Javascript API styles and messes up the zoom slider. Also, don’t forget to assign the appropriate class to the body or some appropriate element so the JSAPI styles get applied!

Specifically, some of the table related styles in Blueprint’s screen.css file are to blame. Generally, I just get rid of all of them but it you want to get surgical about it, the following are the offending declarations:

table {margin-bottom:1.4em;width:100%;}

and

tbody tr:nth-child(even) td, tbody tr.even td {background:#e5ecf9;}