CodeClimber

Deploying a MongoDB powered Node.js app on Windows Azure: my slides

Simone Chiaretta — Fri, 18 Jan 2013 14:23:10 GMT

A few days ago I attended the second event of the newly born Belgian Node.js User Group. The event was about deploying and testing node.js applications and has been hosted in Microsoft Belgium offices near Brussels, thanks to Tom Crombez (aka @artymoony) and Windows Azure.

There were 3 presentations:

Mine, about deploying a MongoDB powered Node.js app on Windows Azure: a walkthrough of the steps needed to deploy the app.
Then another talk on how to build your own “cloud-like” environment on Linux, using systemd. Talk by Ruben Vermeersch.
Finally Julien Biezemans, lead developer of cucumber.js, gave an introduction of BDD and cucumber.js

It was really a nice event, with good catering and good discussion (and for the first time almost 50/50 French speaking / Dutch speaking).

For those who are interested, you can see my presentation online: http://bitly.com/njug_be_azure.

The first step to test azure is of course to create an account. You can do it following that link: http://aka.ms/azurebenug

Tags: node.js, njugbe, presentation

Christmas present for you: Announcing Web.NET Conf 2013 in Paris

Simone Chiaretta — Tue, 25 Dec 2012 18:52:04 GMT

Together with the traditional Christmas and New Year wishes, I wanted to give all European developer a small Xmas present:

Web.NET Conference 2013 will be held in Paris, around the end of May

This year's edition is possible thanks to the help of Rui Carvalho, which already came to talk at last Web.NET Conference.

So, let's look forward to an amazing 2013!!

webnetconf, xmas

How to return a CSV file with ASP.NET MVC

Simone Chiaretta — Thu, 22 Nov 2012 10:48:00 GMT

Continuing with my series of posts inspired by the work done on the Web.NET Conference web site, after telling you why you should not use Boolean fields when modeling your objects, today I want to share with you an ActionResult I wrote to get a CSV from a generic list of object.

I needed to download the list of all attendees in csv format so that I could import them into Excel for doing various free-form analysis: I looked around the net to see if something was available but I found nothing, so I decided to write it myself and do it the most reusable way possible.

I’m not just going to give you the code, but I’d also try and comment the most important part of the class.

Extend ActionResult

Obviously, being used as result returned from an action, the class has to extend ActionResult, and in this case, since what I’m returning is a file, I’m extending FileResult: this provides all the standard file-related tasks, like setting the content type and setting the filename that will be suggested when saving it.

Constructor and declaration

The values for these two properties will be set in the ActionResult’s constructor:

public class CsvActionResult<T> : FileResult
{
    private readonly IList<T> _list;
    private readonly char _separator;

    public CsvActionResult(IList<T> list,
        string fileDownloadName, 
        char separator=',')
        : base("text/csv")
    {
        _list = list;
        FileDownloadName = fileDownloadName;
        _separator = separator;
    }
...

I’m also passing in an optional separator because in many countries the the separator for fields is not a comma, but a semi-column.

Override WriteFile

In order to extend FileResult, you also need to override the WriteFile method, which is the one responsible of getting the value of the file and sending it to the user. The standard implementation just takes a file from the disk and send it to the browser: in this case I have to write to the OutputStream directly the value of my list of objects.

protected override void WriteFile(HttpResponseBase response)
{
    var outputStream = response.OutputStream;
    using (var memoryStream = new MemoryStream())
    {
        WriteList(memoryStream);
        outputStream.Write(memoryStream.GetBuffer(), 0, (int)memoryStream.Length);
    }
}

Discovering the property names at runtime

The csv file needs to have the list of all the columns’ names so that Excel can give a name to it once imported: since the action results accepts any object I needed to find out the name of the property. This was easily done via reflection and passed to a function that writes it in the OutputStream of the response.

foreach (MemberInfo member in typeof(T).GetProperties())
{
    WriteValue(streamWriter, member.Name);
}

The write value method is an utility method that formats the value in the proper way and with the correct separator. I’ll show this later in the post.

Writing each object of the list

After having written the header, always via reflection I get the values of the properties, and write them in the OutputStream.

foreach (T line in _list)
{
    foreach (MemberInfo member in typeof(T).GetProperties())
    {
        WriteValue(streamWriter, GetPropertyValue(line, member.Name));
    }
    streamWriter.WriteLine();
}

If a property is of a complex type, and you still want to export it into the csv file, all you need to do is override the ToString method to format it into a string. Here is the GetPropertyValue method that does the actual work of retrieving the value from object.

public static string GetPropertyValue(object src, string propName)
{
    return src.GetType().GetProperty(propName).GetValue(src, null).ToString()??"";
}

Formatting the property value

Care must be given when writing the actual string otherwise Excel (or any other csv parser) will not be able to get the data correctly: the value must be enclosed in double quotes, and all double quotes inside the value must be escaped. And furthermore the separator has to be different based on the culture of the user, but to make it simple I take the value supplied during the instantiation of the action result.

private void WriteValue(StreamWriter writer, String value)
{
    writer.Write("\"");
    writer.Write(value.Replace("\"", "\"\""));
    writer.Write("\"" + _separator);
}

How to use it

Using the action result is pretty easy: you just create a new instance of the class, and pass it a IList of something. And then return the class in you action method.

public ActionResult CsvList()
{
    var model = CreateUserListViewModel();
    return new CsvActionResult<UserListViewModelItem>(model.Items, "UserExport.csv");
}

Get the complete code

You can get the complete code of the class on this gist. I’ll be creating a NuGet package with binaries and some enhancements soon.

Tags: actionresult , aspnetmvc , extensibility , CSV

Why you should never use a boolean field (use an Enum instead)

Simone Chiaretta — Mon, 19 Nov 2012 09:29:00 GMT

Over the last few months I worked, on my spare time, on a new web development project: the site for the Web.NET Conference. It was a refreshing experience, going back working on custom development on ASP.NET MVC 4 and all the latest bits of technology.

That gave me quite a few ideas for posts, so over the next weeks I'm going to blog about some of the bits and pieces of code that I think are worth sharing with the community, like ActionResults, HtmlHelpers together with my first real-coding experiences with RavenDb.

As first post I’m not focusing on something about a technology, but I want to tell why you should never model a data field as Boolean, and instead start directly with an Enum.

How the problem started

I'm going to tell you what happened during the development of the registration and payment parts of the Web.NET Conference.

I needed to keep track of whether someone has paid or not, so I started modeling that field as a simple boolean value, HasPaid. I also wanted to show them a different message depending on whether they paid or not, to remind them they had to pay in order to get the meal they ordered. To achieve that I checked the value of the HasPaid field: after a while I realized that also people that didn't order a meal had the HasPaid to false, as indeed they didn't pay because they didn't have to.
So in this confirmation screen I also checked whether the total of what they had to pay was different from 0. And it was still manageable.

After a while someone asked if they could pay at the registration desk as in their country PayPal was not operating: so I moved them manually to HasPaid=true and added in the note field that they will pay at the desk, so that their lunch and were taken into account.

Then again something else happened: someone that has already paid unregistered and left what he paid as donation for the conference. Now I needed to filter out their meals, their participation at the conference, but still keep their payment in the count of the donations received, unlike the ones that asked for a refund for which I need to filter out also the payment: this was becoming a nightmare to handle with the original HasPaid field.

On with the refactoring

One evening I sat down, and refactored the payment procedure and all reports to go from a simple boolean to an Enum with the following options:

Undefined
DidntPay (the original HasPaid=false)
NoNeedToPay (for those how didn't reserve a meal or gave no donation)
Paid (the original HasPaid=true)
PaysAtRegistration (for the guys who couldn't pay online)
Refunded (if someone cancels, and wants his money back)

And after the refactoring and making sure all reports and state transitions were using the new Enum, I also had to build a small script to convert all the data inside the RavenDb repository (and this is something interesting I’d probably write a blog post about).

Another example of the same problem

The same problem occurred with the registration status: it started with 2 booleans, IsRegistered and IsWaitlist, then expanded with HasCancelled and WasApprovedFromWaitList and all crazy combinations of boolean expressions to understand his real status, and then, in that very same refactoring session, it all became a more clear and easier with that Enum:

public enum RegistrationStatus
{
    Undefined,
    Confirmed,
    WaitingForPayment,
    Waitlist,
    Cancelled,
    Approved,
    ApprovalNotConfirmed
}

State Machine/Workflow

The benefit of this approach is that both registration and payment became two state machines, and it was much more easy to implement a very simple workflow with the possibility to set allowed and forbidden transition (for example, someone in waitlist couldn’t become “confirmed” without passing from the “approved” status), and action that needs to be done when a given state transition happens. Here is an example of what the transition rules look like: previously with the combination of booleans it was crazy, and very easy to make logical mistakes.

public static class RegistrationFlow
{
    public static void RegistrationStatusTransition(RegistrationStatus newStatus,
        Registration registration)
    {
        switch (newStatus)
        {
        ...
        case RegistrationStatus.WaitingForPayement:
            if(registration.RegistrationStatus!=RegistrationStatus.Undefined &&
            registration.RegistrationStatus!=RegistrationStatus.Approved)
                throw new ArgumentOutOfRangeException("newStatus",
                String.Format("{0} -> WaitingForPayement not allowed",
                registration.RegistrationStatus));
            if(registration.PaymentStatus==PaymentStatus.NoNeedToPay)
                registration.RegistrationStatus = RegistrationStatus.Confirmed;
            else
                registration.RegistrationStatus = RegistrationStatus.WaitingForPayement;
            break;
        case RegistrationStatus.Confirmed:
            if(registration.RegistrationStatus!=RegistrationStatus.Undefined &&
            registration.RegistrationStatus!=RegistrationStatus.WaitingForPayement &&
            registration.RegistrationStatus!=RegistrationStatus.Approved)
                throw new ArgumentOutOfRangeException("newStatus",
                String.Format("{0} -> Confirmed not allowed",
                registration.RegistrationStatus));

            registration.RegistrationStatus = RegistrationStatus.Confirmed;
            break;
        ...
        }
    }
}

Lesson Learned

When I tweeted about this while I was refactoring, someone told me: “Using a boolean is an antipattern”… well… now I experienced it myself.

From this experience, in the future, I’ll never use a Boolean field again, and always start with an Enum, especially with a Document database where migrating data is a bit more complex than with relational databases.

UPDATE: Given the comments received I’d like to clarify a bit my position. I’m not saying booleans are not to be used at all: booleans have value, just not when the the thing you are trying to model is a state and not just a real/physically boolean value.

Tags: webnetconf , boolean , enum , architecture

OpenROV at Node.js Conf Italy and Maker Italy

Simone Chiaretta — Tue, 13 Nov 2012 11:09:39 GMT

On the 11 of November I had the pleasure to present at the Node.js Conference Italy the work I’ve been doing with Dominik and a bunch of other guys in the San Francisco area on the “brain” of the robotic submarine called OpenROV.

On my way back from Brescia I stopped by at the first Italian Maker Faire, held in the big expo area of Milano Rho, where I wandered among stands full of flying drones, biped robots, 3D printers, FabLabs and electronics shops.

Together with web development, the makers and open hardware movement is something I’m getting interested in, and after few months dedicated totally to web development, this was a weekend totally devoted to these two new interests.

Slide and resource of my OpenROV presentation at Node.js Conference

During the 30 minutes presentation I went over the physical design of the OpenROV, the reasons why it has been build in the first place, and an overview of the architecture of the software that runs on the small board inside the robot itself.

I was the only one doing a presentation in JavaScript, using Reveal.js, which was shocking being it a conference on JavaScript: the slides are available both as JavaScript presentation but also published on Slideshare.

On my other blog about all things HW and makers I also wrote a blog post with a bit more of resources and a longer commentary of the event.

The Italian Maker Faire

On my way back home, after the Node.js conference hackathon, I spent a few hours wandering among the stands at Makers Italy: the maker movement is invading Italy too… finally!

Not only robots and drones, but also a lot of stands on digital fabrication tools (3D printers above everything) and of small makers’ founded companies making various items like custom skateboards, guitars, bags, jewelries and so on.

Not sure if that movement will bring innovation or it’s just yet another trend, but for the moment it seems like a lot of people are getting interested, building tools for makers, and it won’t be long before digital fabrication tools will land in every house. Already now, 3D printers are less expensive of a low level PC 10 years ago, and I guess they’ll reach the cost of an entry level laptop.

Again on my drones&rovs blog I wrote my impressions and a small review of the stands I found more interesting.

Tags: makersitaly, nodejs, openrov, conference

Web.NET Conference: find it on social media

Simone Chiaretta — Thu, 04 Oct 2012 16:27:55 GMT

Apart from the obvious twitter and facebook, the Web.NET Conference is using a few specific social networks. We are also on:

Geekli.st – A social network for “geeks”
OleaPark – A conference specific networking app
Lanyrd – A conference social directory

I’m going to explain a bit more what they are, and for we have decided to use them.

Geekli.st

Probably I should have added geekli.st in the first line of this post, next to twitter and facebook after the adjective “obvious”. If you are a developer you should at least know what it is, or already have a profile over there (if you don’t, you can join geekli.st). Basically it’s social network were developers can share their accomplishments, talk about what they are building and doing but always staying on “geek talk”. But it’s also becoming the new way of seeking and offering jobs.

Geekli.st is also one of the main sponsors of the conference (they also offered T-Shirt for everyone) and it might be that Christian Sanz, the CTO and co-founder of Geekli.st comes and give a presentation at the conference.

You can find the Web.NET Conference on Geekli.st at: https://geekli.st/WebNETConf

OleaPark

This Berlin-based French startup has built a new way for people attending conferences to connect one another: you go to the event page, you download the app (iPhone, Android and soon mobile site) and can see who is attending the conference, their profiles and if you see someone that can be a interesting person, you can contact him via the app. And on the day of the event people can checkin at the conference, and you can see how is there and start talking to them. To understand better, there is a video that explains everything on their site.

You can join the conference on OleaPark at: http://oleapark.com/events/4ff30c8f7c93dd14e5000002

Lanyrd

And finally the Web.NET Conference is also on Lanyrd. That is yet another way to see who is attending the conference, but also to see the history of each speaker and get a feeling of the type of audience that will be at the conference. And if you are someone that easily forget dates and times, you can add the conference’s schedule to your calendar.

Lanyrd also provides a nice mobile-optimized version of the agenda.

If you use Lanyrd, you can join the event at: http://lanyrd.com/2012/webnet12/

Twitter and Facebook

Even if “obvious” the conference is on twitter and facebook, so don’t forget to follow @webnetconf to get real-time info and updates on the conference, like the conference’s page on Facebook and join the FB event.

Tags: webnet12, conference, twitter, geeklist, social media

Web.NET European Conference: sold out in 2hrs and now the agenda is available

Simone Chiaretta — Thu, 27 Sep 2012 09:31:50 GMT

I have to say that lately all my spare time has been dedicated to the organization of the Web.NET Conference: I firmly believe that the future of web development will move away from the enterprise features and the needless over-engineering typical of the last decade. That’s why I’m putting so much effort in this conference. And I’m super happy of how it’s rolling out.

Registration: Sold out and waitlist is open

We opened registration the 18 of September, at midday, and by 2:30PM all the 120 places available have been given out: that means 120 seats in 2:30. The previous record for the other conference I organized was 120 seats in one day, and it was already a big accomplishment.

At the moment only the waitlist is open, and there are already 40 persons in it: from experience we usually recall 40 people from the waitlist (if people registered are nice and tell us if they planning on not coming anymore), so if you register quickly chances are you might take part in the conference anyway.

Agenda

I want to thank all the people that voted during the month of August as they really helped shape the conference: we have received 45 proposals from 30 speakers all of which where super interesting, and would have been really difficult for us to choose the 20 sessions for the agenda. Here is the beautiful design of the agenda, designed by the guys of GreenBubble, an Italian web agency that jumped both feet together with us on this project (click on the image to read the agenda):

There will be a lot of international speakers and they’ll talk about WebAPI, REST, OWIN, advanced JavaScript frameworks, and more: all topics strictly related to “simplicity” and lightweight approach in building web applications.

Now 3 more weeks and the conference will kickoff: it will be a busy period, but really looking forward to meeting in person everyone that made this possible: the speakers, the sponsors and the attendees.

Tags: webnet12, conference, future of web

Vote for the sessions you want to attend at the Web.NET Conference

Simone Chiaretta — Mon, 06 Aug 2012 12:48:13 GMT

Over the month of July, 29 speaker submitted 44 presentations' proposals. But we have only 19 slots, so even limiting to one session per speaker we will not be able to accept all the speakers that submitted a proposal.

Today we are opening the voting phase: till the beginning of September you’ll be able to vote for the 5 sessions you’d like to attend to at the Web.NET Conference on the 20 October.

Speakers are coming from all Europe (and beyond), like Pierre Spring from Switzerland, Niels Hartvig from Umbraco, Jakob Mattsson from Sweden, Maarten Balliauw, Kris van der Mast and Jef Claes from Belgium, Ayende from Israel, Christian Horsdal from Denmark (first proposal received), Robert Mühsig from Germany. Of course also a lot of Italian, like Roberto Messora, Raffaele Rialdi, Massimiliano Mantione (which is now working on the Chrome’s V8 Javascript compiler) and many more.

Which topics have been proposed?

Just to give you a taste of what has been proposed, here is a quick list of the topics:

ASP.NET Web API
NancyFx, OpenRASTA, FubuMVC
HTML5, CSS3, Responsive Design
Owin, SignalR
Backbone.js and Knockout.js
Django, Node.js, Sinatra
Orchard, Umbraco and Sharepoint
Azure and cloud computing in general
Javascript performance tips (from someone that builds the V8 compiler for Chrome)
and much more

To get the full list of speaker and topics, just go the Web.NET Conference web site, login with your Twitter or Facebook account, and vote for the 5 sessions you would like to attend.

The voting will stay open till beginning of September. And then we’ll open the registrations to the conference.

Tags: webnet12, conference, voting

Node.js Conference: call for papers

Simone Chiaretta — Thu, 02 Aug 2012 13:33:55 GMT

Not only .NET, but Node.js too.

There are just 4 days left for submitting your proposal for the Web.NET Conference, but in this post I wanted to share a bit of love for the Node.js conference, happening in Brescia (if you are not from Italy it’s more or less near Milano), in November.

They have opened the Call For Papers that will stay open till the 10 of September.

If you are doing Node.js, and you want to share some of your knowledge, this is the conference for you: to submit a proposal you have to fork the GitHub repository of the conference, edit the json file adding the title of your talk, and your personal details, and then send a pull request.

So, what are you waiting: submit yours!!

PS: I submitted mine too (hint, will be about OpenROV and its usage of Node.js to control it).

Tags: node.js, nodejsconf, WebDeBS

Open Hardware: Drones and ROVs, artistic project

Simone Chiaretta — Tue, 24 Jul 2012 21:35:09 GMT

You may have noticed a bit of emptiness in this blog in the last few months: I’m not apologizing for not posting, just explaining what I’ve been doing in the past months (and probably doing in the next ones too).

Web.NET European Conference

Probably already obvious to the most loyal readers, I’m organizing with the help of Ugo Lattanzi the First European Web.NET Conference. It was a busy period and lots of stuff to do, but it was rewarding: we released a brand new website, we’ve got some great sponsors, and we are running the call for presentations (that at the time of writing had 27 proposals, already 6 more than the available slots). And in a few weeks we are also launching the voting for the proposals received, so a bit more of work to do on that side.

But this was not what I really wanted to talk about. I wanted to introduce you to my other hobbies: playing with Arduino, Open Hardware, Electronics for an artistic project I’m doing with Daniela and building RC/autonomous vehicles.

Les Paysages Pulsionnels

This is something I’ve been working on since last summer: Daniela and I have been working on an artistic project that involved the interaction of persons with a room via the usage of sonars, and other biometric sensors. All is developed with Arduino and Processing.

In June we also presented our project, actually the first step of the project, involving only sonars and sounds, at an art exhibition here in Bruxelles.

This project was extremely useful, because I started getting a bit more deeper into electronics and facing problems I never faced developing “only” software, like things that works with a 3m cable, but not on 10m one. And I also got more and more experienced with soldering, which was something that always scared me.

If you are interested in our artistic project, how our first exhibit went and all my testing with sonars, you can go on and have a look at the site we made for our project: http://paysagespulsionnels.wordpress.com/

I’ll be updating it when we start working on the following steps of the projects, and I will also post some tutorials and the code used for the project.

Drones and ROVs

But my usage of Arduino is not limited to this artistic project: I’m also following very closely (and already got everything I need but still have to find the time to build it) the development of ArduCopter, a multicopter powered by a custom Arduino board that can either fly controlled by a RC transmitter or can fly autonomously as a drone, doing automated missions via waypoints or flying controlled by a base station or via normal joypad.

On the sky, but also beneath the surface of the water. This time more actively contributing, I’m following the development of OpenROV, an underwater submarine, remotely controlled by a web browser via an embedded web server running Node.js on a BeagleBone.

I’m also proposing a speech for the NodeJsConf in Brescia this November about the Node.js embedded code that drives the OpenROV.

This is giving me a lot of experience and knowledge on how RC stuff works, batteries, motors, embedded development and Node.js coding.

I’ve setup a blog with a build log of both the Arducopter and the OpenROV. If you are interested on how they are proceeding you should check it out.

These, together with the fact that at work I’m not doing a lot of development but mainly team management, were the reasons why I’m slowing down my production of .NET web development related contents.

Tags: arduino , arducopter , OpenROV , PaysagesPulsionnels