DNUG Reactive Framework Presentation

On December 17th (2009) I gave a talk to my local .NET user group about the Microsoft Reactive Extensions for .NET

The talk seemed to go down well - a PDF export of the slides from KeyNote is available if you're interested

Here's a brief outline of what I talked about:

Note: I had a recurring theme throughout the presentation that shorter code is better. I had random slides thrown in with quotes from programming "celebrities" to keep trying to push the point. I did this because I personally believe in it, and also because being able to do more with less code is one of the big benefits of the Reactive Framework.

As I've met more than a few developers who are still running .NET 2.0 on VS2005, I started by giving a brief recap on the C# 3.0 language features that Rx makes heavy use of (lambdas, linq, and so forth)

I then did a quick overview defining exactly what Asynchronous programming is, and why you'd want to do it (Rx is all about asynchronous programming after all)

With the overviews out of the way, I talked a bit about the IObservable interface and how it related to IEnumerable, and showed a few short code snippets of code using Rx (looking surprisingly the same as ordinary Linq), and some diagrams showing the timeline of things that happen when using both IEnumerable and IObservable

I then cut to a demo. Sample code shown in the demo is available as on Google Code and I'm placing it under the creative commons by attribution license. You don't have to provide attribution (it's a code sample!), but I can't find a CC license other than public domain that doesn't require attribution.

Most of the demo focused on the WcfClient and WcfServer projects - they're the most interesting, so I'd suggest looking at those if you're interested.

I followed up with a few more slides containing other tidbits (such as the fact that you get a backport of the .NET 4 parallel task library for free with Rx), and some links.

Enjoy!

Programming podcast roundup

When the stackoverflow podcast first launched, I downloaded it and gave it a listen. I enjoyed it, and I was sick of listening to the same old music when going running... and so, my podcast-listening-habit was born.

Thus far I've been stuck in the microsoft-centric technology podcasts. This not because I'm a microsoft shill, but because I haven't been able to find any non-microsoft-centric podcasts out there.

At any rate, here's the ones I regularly listen to, ranked by preference.

1. The Stack Overflow Podcast

Admittedly I'm biased as this was the first podcast I listened to, and I've been following it since day one. Even had this not been the case, I think I'd still rank it highly.
The SO podcast primarily consists of Jeff Atwood and Joel Spolsky chatting about the stackoverflow site, and programming/IT topics in general. Major topics are either pulled from the SO site, from reader questions, or often based on current events, or whatever they're each up to.
Even if you think Joel and Jeff are a pack of jumped up blowhards (as many no doubt do), they're still really entertaining to listen to. Both speak well and have a wide variety of experience to draw on (Joel in particular is the king of 'back in my day' type stories, which are usually very interesting). They also complement eachother well which makes for good listening.
I like the fact that the show is centered around them and on the stackoverflow site. They'll occasionally have third party participants on the show, but the majority of shows are just Jeff and Joel. I find this helps you feel like you "know them" better, rather than that they're just interviewers or reporters.
Finally, the SO podcast gets a big bonus for not being full of annoying ads. It has a small bit at the beginning and end from IT conversations, who provide their hosting, and that's it. It typically runs for about an hour.

2. Hanselminutes

Hanselminutes is Scott Hanselman interviewing people about technology. Every week there's a different guest, always talking about some recent technology. Most (but not all) are microsoft based, which is no doubt a side effect of Scott being a microsoft employee.
This does however have it's upsides, as you'll get to find out stuff by hearing it directly from other microsofties that come on the show, rather than hearing things through the rumourmill / blogosphere / reddit.
Hanselminutes is very well produced, and Scott really knows how to do a good interview. Most of the guests are top-notch, and often the tech talk gets pretty deep, which IMHO is great, as it provides the substance of the show.
Recently the podcasts took a bit of a detour, while Scott was in south africa - and interviewed some of the local people about non-technical things, and his family (his wife is from Zimbabwe). I really enjoyed these, as it was really cool to get a bit of insight into the way things are in some other (non-westernised) countries.
Hanselminutes has some advertising at the beginning, and typically has a single "spliced in" ad in the middle. These tend not to be too long though. The show usually runs for half an hour.

3. The Australian Gamer Podcast

OK, this is not programming related at all, but I'm an ex gamer so I like to keep up with that scene periodically.
At any rate, Matt and Yug (the hosts) are _very_ funny (in a crude guy-humour kind of way. It's R18, you have been warned.)
I know of many people who have little to no interest in cars, yet enjoy watching Top Gear, because the presenters simply put on a really great entertaining show.
In my humble opinion at least, the AG podcast is similar. I played it in the car while driving somewhere with my girlfriend (who is not a gamer in the slightest), and she said that apart from all the swearing, it was actually pretty good. That's high praise :-)

4. Herding Code

Herding code is a "technology round-table" run by K. Scott Allen, Kevin Dente, Scott Koon and Jon Galloway, who are all either microsofties, MVP's, or otherwise working using the microsoft technology stack. It's usually just them sitting around chatting (4 people is more than enough to keep a conversation going), with occasional interviews.
It's not as professionally produced as some other podcasts, but it does have a really good friendly atmosphere. You feel like these guys are good mates, and they'd be sitting around talking about this stuff anyway, recording or not.
I really like this, as you feel like you get to know them a lot more, which keeps you engaged.
Herding code doesn't have any sponsored introductions, or inline ads at all. This is awesome, but I wonder if it's just because the show hasn't picked up any yet?

5. Deep Fried Bytes

DFB is another interview driven show, run by Chris Woodruff and Keith Elder. It's kind of similar to hanselminutes, in that there's a guest being interviewed or talked to every show, but Chris and Keith bring their own brand of humour and atmosphere, and also have great character. The "feel like you know them" factor is high.
My one complaint about DFB is that the format thus far seems to be like this: 1) Go to a conference and record interviews with conference speakers and attendees. 2) publish interview as a podcast, repeat until you've run out of interviews, then go to another conference
This is not in and of itself bad, but when you're putting out shows in february which were recorded at the PDC in october, it starts to wear thin a bit.
DFB doesn't have any sponsored intros or ads, and runs for around 45 minutes.

6. .NET Rocks!

DNR is the granddaddy of the tech podcast. Carl Franklin and Richard Campbell are currently on show Number 432, and put out new ones every week like clockwork.
It's another interview-centric show, focused around the Microsoft .NET ecosystem. It sometimes has a bit of an overlap with Hanselminutes (the same guests will appear on each show in quick succession when a new technology is coming out of MS), but it's different enough to always be worth listening to both.
The production quality is top notch (the best out of all the podcasts I've heard). Carl is a musician, and his obvious knowledge of all things audio shows itself here. Apart from the fact that they're talking about .NET programming, you could easily believe this was a show coming from your local radio station's best morning dj crew.
I feel kind of bad putting DNR down the bottom of the list, as it really is a very good podcast, but sadly it is the one I will listen to after I've heard all the others. This is more a testament to how much I like the others than an indictment against DNR. Carl and Richard have been doing this for a long long time, and they're very good at it.
The main thing that bugs me about DNR is actually the ads. They have a 2 minute sponsored intro, then usually 2 or 3 ads spliced into the middle of the show. The ads tend to be longer than on other podcasts, and more intrusive. Shows tend to run between 45 minutes to an hour, but if you skip the ads and the leadout, it's about ten minutes less. If you know of any other good tech podcasts, just drop a comment! Cheers, Orion

Duplicate Line in Visual Studio

Visual Studio ships with many features built in. "Duplicate the current line" doesn't appear to be one of them for some strange reason.

CodeRush Express ships with a "duplicate line" function, but it's WAY too clever for it's own good. It tries to work out whether you're duplicating a line with a variable, function, etc, and act accordingly. If it can't understand your line (perhaps it's just a string), then it FAILS. Unfortunately it only understands about 40% of actual lines of code, so this severely limits it's usefulness.

This is stupid. I just want the equivalent of "copy/paste the current line be done with it", so without further ado, here's a macro to do it. You can then bind a keyboard shortcut to the macro, and get on with more important things.

Imports System
Imports EnvDTE
Imports EnvDTE80
Imports EnvDTE90
Imports System.Diagnostics

Public Module Misc
    Sub Duplicate_Line()
        DTE.UndoContext.Open("Duplicate Line(s)")
        Try
            Dim ts As TextSelection = DTE.ActiveDocument.Selection
            Dim epStart As EditPoint = ts.TopPoint.CreateEditPoint()
            Dim epEnd As EditPoint = ts.BottomPoint.CreateEditPoint()

            Dim lineText As String = epStart.GetLines(epStart.Line, epEnd.Line + 1)

            epEnd.EndOfLine()
            epEnd.Insert(Environment.NewLine)
            epEnd.Insert(lineText)

            ts.MoveToLineAndOffset(epEnd.Line, epStart.LineCharOffset())
        Finally
            DTE.UndoContext.Close()
        End Try
    End Sub
End Module

PS: Why can't I write VS macros in C#? VB just looks so ugly :-(

Windows 7 beta 1: sound does not work on Macbook Pro (RealTek HD Audio)

This post is googlebait: I couldn't find the solution for this on google, so here's how I solved it. Hopefully others will be spared the messing around.

After installing windows 7 beta 1 (7000) on my macbook pro, and installing the bootcamp drivers off the Leopard Disc, as well as The vista 2.1 bootcamp update, everything worked very nicely... Except sound.

Win7 detected "High Definition Audio Device" and everything looked like it should have worked, but no sound came out of the speakers.

After much mucking around, here's what I did:

Go into the leopard drivers folder. There should be a directory called Drivers, and under that is a file called RealTekSetup.exe. If you try run this normally, it will fail.

What I did next was:

Right click it, and select Troubleshoot Compatibility

Click Next and wait for it to finish 'Detecting Issues'

Select The program Worked in earlier versions of windows...

Select Windows Vista

Click Next a few times, let the Realtek installer run, reboot, and Presto!

As for win7 itself? Well, the beta is faster, nicer, and all around better than vista. I'll never go back. They didn't do a good enough job of copying the dock... but it's still miles ahead of vista, and that's another blog post.

Byebye!

Embedded IronRuby interactive console

Screenshot!

What this is, is a small dll which you can add to any .net winforms project. When run, it brings up the interactive console, and you can poke around with your app. It's running live inside your process, so anything your app can do, it can do. I thought this was kind of cool :-)

How to get it going:

1. Download and build IronRuby by following the instructions on IronRuby.net - I built this against IronRuby SVN revision 153. As of RIGHT NOW the current revision is 154 which doesn't build.
2. Download the Embedded IronRuby project from the following URL - you can use SVN to check it out directly from there. (I'm assuming familiarity with SVN in the interests of brevity)
   http://code.google.com/p/orion-edwards-examples/source/browse/#svn/trunk/dnug/ironruby-presentation/EmbedIronRuby
3. Open the EmbeddedIronRuby/EmbeddedIronRuby.sln file in visual studio, and remove/add reference so that it references IronRuby.dll, Microsoft.Scripting.dll, Microsoft.Scripting.Core.dll, and IronRuby.Libraries.dll. These will be in the IronRuby build\debug folder that you will have built in step 1.
4. Compile!
5. For some reason, when you compile, Visual Studio will only copy IronRuby.dll, Microsoft.Scripting.dll and Microsoft.Scripting.Core.dll to the bin\debug directory. It also needs IronRuby.Libraries.dll in that directory (or in the GAC) to run, otherwise you get a stack overflow in the internal IronRuby code when you run it.
   The joys of alpha software I guess :-)
6. Run the app and click the button!

You can also add this embedded console to your own app. Just stick all the dlls in your app's folder (or the GAC) so it can see them, add a reference to EmbeddedRubyConsole.dll, and in your app do this: new EmbeddedRubyConsole.RubyConsoleForm().Show();

Credit: Some of the 'plumbing' code (the TextBoxWriter and TextWriterStream) come from the excellent IronEditor application. Full credit to and copyright on those files to Ben Hall. Thanks!

IronRuby Presentation!

I recently gave a presentation to my local .NET user group about IronRuby.

Click on the image to download the slides as a PDF file.
Note: This was exported from keynote with speaker notes, which I've revised slightly since giving the presentation.

As part of this, I demoed a small library I wrote which gives you a live interactive ruby console as part of your running app.

Basically it lets you poke around your program and modify things while it's running. I'll post the code and notes about that shortly

Ruby Unit Converting Hash

I'm currently working on a project where I need to convert from things in one set of units to any other set of units ( eg centimeters to inches and so forth)

I had a bunch of small helper functions to convert from X to Y, but these kept growing every time we needed to handle something which hadn't been anticipated.

This kind of thing is also exponential, as if we have 4 'unit types' and we add a 5th one, we need to add 8 new methods to convert each other type to and from the new type

A few hours of refactoring later, I have this, which I think is kind of cool, and will enable me to delete dozens of small annoying meters_to_pts methods all over the place.

Disclaimer: This is definitely not good OO. A hash is not and never should be a unit converter. In the production code I will refactor this to build an actual Unit Converter class which stores a hash internally :-)

# Builds a unit converter object given the specified relationships
#
# converter = UnitConverter.create({
#  # to convert FROM a TO B, multiply by C
#  :pts    => {:inches => 72},
#  :inches => {:feet   => 12},
#  :cm     => {:inches => 2.54, 
#              :meters => 100},
#  :mm     => {:cm     => 10},
# })
#
# You can then do
#
# converter.convert(2, :feet, :inches) 
# => 24
#
# The interesting part is, it will follow any links which can be inferred
# and also generate inverse relationships, so you can also (with the exact same hash) do
#
# converter.convert(2, :meters, :pts) # relationship inferred from meters => cm => inches => pts
# => 5669.29133858268
#
class UnitConverter < Hash
  
  # Create a conversion hash, and populate with derivative and inverse conversions
  def self.create( hsh )
    returning new(hsh) do |h|
      # build and merge the matching inverse conversions
      h.recursive_merge! h.build_inverse_conversions
      
      # build and merge implied conversions until we've merged them all
      while (convs = h.build_implied_conversions) && convs.any?
        h.recursive_merge!( convs )
      end
    end
  end
  
  # just create a simple conversion hash, don't build any implied or inverse conversions
  def initialize( hsh )
    merge!( hsh )
  end
  
  # Helper method which does self.inject but flattens the nested hashes so it yields with |memo, from, to, rate|
  def inject_tuples(&block)
    h = Hash.new{ |h, key| h[key] = {} }
    
    self.inject(h) do |m, (from, x)|
      x.each do |to, rate|
        yield m, from, to, rate
      end
      m
    end
  end
  
  # Builds any implied conversions and returns them in a new hash
  # If no *new* conversions can be implied, will return an empty hash
  # For example
  # {:mm => {:cm => 10}, :cm => {:meters => 100}} implies {:mm => {:meters => 1000 }}
  # so that will be returned
  def build_implied_conversions
    inject_tuples do |m, from, to, rate|
      if link = self[to]
        link.each do |link_to, link_rate|
          # add the implied conversion to the 'to be added' list, unless it's already contained in +self+,
          # or it's converting the same thing (inches to inches) which makes no sense
          if (not self[from].include?(link_to)) and (from != link_to)
            m[from][link_to] = rate * link_rate 
          end
        end
      end
      m
    end
  end
  
  # build inverse conversions
  def build_inverse_conversions
    inject_tuples do |m, from, to, rate|
      m[to][from] = 1.0/rate
      m
    end
  end
  
  # do the actual conversion
  def convert( value, from, to )
    value * self[to][from]
  end
end

I'm not sure if deriving it from Hash is the right way to go, but it basically is just a big hash full of all the inferred conversions, so I'll leave it at that.

---

Update

Woops, this code requires 'returning' which is part of rails' ActiveSupport, and an extension to the Hash class called recursive_merge!, which I found on an internet blog comment somewhere (so it's only fitting that I share back with this unitconverter)

Code for recursive_merge

class Hash
  def recursive_merge(hsh)
    self.merge(hsh) do |key, oldval, newval|
      oldval.is_a?(Hash) ? 
        oldval.recursive_merge(newval) :
        newval
    end
  end
  
  def recursive_merge!(hsh)
    self.merge!(hsh) do |key, oldval, newval|
      oldval.is_a?(Hash) ? 
        oldval.recursive_merge!(newval) :
        newval
    end
  end
end

Code for returning

class Object
  def returning( x )
    yield x
    x
  end
end

HaveBetterXpath

I'm rspeccing some REST controllers which return XML, and wanting to use XPath to validate the responses.

I came across this

http://blog.wolfman.com/articles/2008/01/02/xpath-matchers-for-rspec

Thanks to him. It worked nicely (couldn't be bothered messing about with hpricot to get that to go), but I didn't like the API as much as I could have.

Example of that API:

response.body.should have_xpath('/root/node1')
response.body.should match_xpath('/root/node1', "expected_value" )
response.body.should have_nodes('/root/node1/child', 3 )

I didn't like the fact that there were 3 distinct matchers, and that match_xpath didn't work with regexes. I re-worked it, so the API is now

response.body.should have_xpath('/root/node1')
response.body.should have_xpath('/root/node1').with("expected_value") # can also pass a regex
response.body.should have(3).elements('/root/node1/child') # Note actually extends string class and uses normal rspec have matcher

Extending the String class to support elements(xpath) is a win also because it lets you do things like

response.body.elements('/child').each { |e| more complex assert for e here }

Without further ado, new code here:

# Code borrowed from
# http://blog.wolfman.com/articles/2008/01/02/xpath-matchers-for-rspec
# Modified to use one matcher and tweak syntax

require 'rexml/document'
require 'rexml/element'

module Spec
  module Matchers

    # check if the xpath exists one or more times
    class HaveXpath
      def initialize(xpath)
        @xpath = xpath
      end

      def matches?(response)
        @response = response
        doc = response.is_a?(REXML::Document) ? response : REXML::Document.new(@response)
        
        if @expected_value.nil?
          not REXML::XPath.match(doc, @xpath).empty?
        else # check each possible match for the right value
          REXML::XPath.each(doc, @xpath) do |e|
            @actual_value = e.is_a?(REXML::Element) ? 
              e.text : 
              e.to_s # handle REXML::Attribute and anything else
  
            if @expected_value.kind_of?(Regexp) && @actual_value =~ @expected_value
              return true
            elsif @actual_value == @expected_value.to_s
              return true
            end
          end
          
          false # our loop didn't hit anything, mustn't be there
        end
      end
      
      def with_value( val )
        @expected_value = val
        self
      end
      alias :with :with_value

      def failure_message
        if @expected_value.nil?
          "Did not find expected xpath #{@xpath}"
        else
          "The xpath #{@xpath} did not have the value '#{@expected_value}'\nIt was '#{@actual_value}'"
        end
      end

      def negative_failure_message
        if @expected_value.nil?
          "Found unexpected xpath #{@xpath}"
        else
          "Found unexpected xpath #{@xpath} matching value #{@expected_value}"
        end
      end

      def description
        "match the xpath expression #{@xpath}, optionally matching it's value"
      end
    end

    def have_xpath(xpath)
      HaveXpath.new(xpath)
    end
    
    # Utility function, so we can do this: 
    # response.body.should have(3).elements('/images/')
    class ::String
      def elements(xpath)
        REXML::XPath.match( REXML::Document.new(self), xpath)
      end
      alias :element :elements
    end

  end
end