10 May 2014

throw vs throw ex vs wrap and throw in c-sharp

I've come across the throw vs throw ex 'debate' a few times, even as an interview question, and it's always bugged me because it's never something I've worried about in my own c# code.

background

So here's a typical example of the throw vs throw ex thing: https://stackoverflow.com/questions/730250/is-there-a-difference-between-throw-and-throw-ex

Basically it revolves around either messing up the line numbers in your stack trace (throw ex;) or losing an chunk of your stack entirely (throw;) - exception1 and 2 respectively in this nice clear answer http://stackoverflow.com/a/776756/10245


the third option

I've just figured out why.

Because in my own code, whenever I catch and re-throw I always wrap another exception to add more context before rethrowing, and this means you don't have either of the above problems. For example:

private static void ThrowException3() {
try {
DivByZero(); // line 43
} catch (Exception ex) {
throw new Exception("doh", ex); // line 45
}
}

Exception 3:
System.Exception: doh ---> System.DivideByZeroException: Division by zero
  at puke.DivByZero () [0x00002] in /home/tim/repo/puker/puke.cs:51 
  at puke.ThrowException3 () [0x00000] in /home/tim/repo/puker/puke.cs:43 
  --- End of inner exception stack trace ---
  at puke.ThrowException3 () [0x0000b] in /home/tim/repo/puker/puke.cs:45 
  at puke.Main (System.String[] args) [0x00040] in /home/tim/repo/puker/puke.cs:18 

Obviously 'doh' would be something meaningful about the state of that function ThrowException3 in the real world.

Full example with output at https://gist.github.com/timabell/78610f588961bd0a0b95

This makes life much easier when tracking down bugs / state problems later on. Particularly if you string.format() the new message and add some useful state info.

08 March 2014

Why publish open source when you are commercial?

Why open source your commercial projects?
  • Forces you to decouple them from other internal systems.
  • Encourages thinking in terms of reusable modules, which is better for internal reuse just as much as public reuse.
  • Possibility of contributions to systems useful to your business by others.
  • Easier reuse within your organisation (the public internet is a better search and sharing system than any internal systems).
  • Reputation advantages, the best coders often like to work in open and forward-thinking companies, and having public shared code is a great sign of such an organisation.
Do it early
  • Preferably push your very first commit straight to github.
  • Do it before it has a chance to be tightly coupled to internal systems, otherwise you'll have to unpick it and it will be less decoupled from day one, and inertia might mean that in spite of the best intentions you then never publish it.
  • You'll have it in mind that every commit is public from day one, avoiding adding internal config etc and forcing you to factor it out into config which is all round a good thing.
  • Don't wait for your code to be perfect, there are compromises in all code and sharing something imperfect is better than sharing nothing.

Worried about the brand?
  • Commit under personal email addresses and push to personal github accounts. You can always setup a corporate github account later when you are feeling more confident.

Of course I'm not saying you should open source everything, for example your core product's codebase should probably not go on github if you are a product company!

--

Be brave, be open.
Props to Tom Loosemoore

10 February 2014

Bash command line editing cheat sheet

https://www.gnu.org/software/bash/manual/bashref.html#Readline-Interaction
  • ctrl-a/e start/end of line
  • alt-f/b forward/back a word
  • ctrl-w/alt-d delete to start/end of word
  • ctrl-shift-_ undo (i.e. ctrl-underscore)
  • ctrl-y paste (yank) deleted text
    • alt-y paste older deleted text instead
  • prefix with alt+digit (0-9) to do multiple, e.g. delete two words
    • start with alt-minus to go backwards

Just a few notes I threw together for my own benefit. I finally got around to learning a bit more about editing commands on the Linux shell / terminal.

03 February 2014

Converting kml to gpx with python

Today I wanted to geo-code some of my photos.

I have an SLR digital camera (no gps of course), and an android phone. I recorded a track with My Tracks from google on the phone. (Not entirely recommended but works). I then fired up digikam to run the geo-correlation and add lat-long to the exif of the files only to discover digikam doesn't know how to read kml. Fooey.

 

I looked to gpsbabel, but it apparently can't handle this style of kml file, as differentiated by the coordinates being in the following style of markup:

<gx:Track>
<when>2014-01-25T18:00:13.955Z</when>
<gx:coord>-1.885348 50.769434</gx:coord>
<when>2014-01-25T18:00:14.565Z</when>
<gx:coord>-1.885193 50.769328 53.20000076293945</gx:coord>
<when>2014-01-25T18:00:58.566Z</when>


So I wrote a python script to munge it into gpx shape:

https://gist.github.com/timabell/8791116

This can be run as follows:

./kmlToGpx.py "25-01 12-48.kml" > "25-01 12-48.kml.gpx"

And worked a treat for me.

After I'd done this I discovered my pet tool gpsprune can open the new style kml. (I forked gpsprune a while ago and added a minor feature) However I'm glad to have a command-line tool as I have hundreds of tracks I want to convert.

Incidentally the phone can automatically sync the tracks to google drive, which is kinda handy and then you can download them from the site etc.

07 January 2014

Returning to commercial ASP.NET from Ruby on Rails

Why ASP.NET again after all the noise I made about Ruby on Rails? After a brief stint with commercial Ruby on Rails development I should explain why I've decided my next gig will be an ASP.NET project. In short: currently almost all the Rails work available is in London for digital agencies and start-ups, demanding on-site full time presence, and I burned out doing 3 hours a day commuting in less than half-a-year. This is not a sustainable business plan.

The emphasis on start-ups and agencies bodes well for the commercial future of Rails as many of these projects will bloom into large systems needing continuing development. I will continue to use Rails for my own projects (such as the in-progress https://github.com/timabell/symbol-library ). But for me the market in the Reading area seems too quiet to make a business success from just Rails. The final straw was being formally offered a rare local permanent Rails job working with all my favourite open source technologies (Rails, Postgres, Linux etc) only to be handed an employment contract with less job security, rights and benefits than a contractor would have. This confirmed my growing understanding of the local market not being suitable at this time.

So my updated plan of action is to return to providing programming services to the vibrant .NET market in the local area, whilst also working on a database migration product for the same market (still in the research phase), but to keep my hand in with Ruby on Rails with personal projects.


This article is for my Linked In audience, if you want to become part of my network or learn more about my professional services send me a message or invite here: http://www.linkedin.com/in/timabell

04 December 2013

Getting rails 4 up and running with rbenv on Ubuntu 13.10

Brain dump warning!

This is a follow up to http://timwise.blogspot.co.uk/2013/05/installing-ruby-2-rails-4-on-ubuntu.html and is just a list of steps needed to get a clean install of Ubuntu up to speed with an existing site.
  • get a project (includes a .ruby-version file for rbenv, and a Gemfile for bundle)
    • git clone git@github.com:timabell/symbol-library.git
  • sudo apt-get install libssl-dev libreadline-dev
  • rbenv install x.x.x-xxxx
    • autocompletes, yay!
    • .. or better still reads from .ruby-version I think so you can just run `rbenv install` if you are in the project folder
  • gem install bundler
    • from the right directory so done for right ruby version
    • rbenv rehash
  • bundle
    • will install all the gems for the project
  • don't sudo apt-get install rbenv ~ doesn't provide sufficiently up to date ruby
  • gem install rails --version 4.0.2 --no-ri --no-rdoc ~ don't need this when you have a gem file with rails in it, bundle will do it for you
  • sudo apt-get install nodejs
    • for javascript runtime (rails server throwing an error without this)
  • bundle exec rails server
  • bundle exec rails console
    • needs readline (see above)
Other stuff I like in my install
This is mostly for my own reference but maybe it'll help someone else out.

25 May 2013

Unfinished hyperlinks - add a todo

Just a quick post;

href="#"   ==>   href="#todo"

I'd like to promote a change to the habit of using '#' as the placeholder for a the url of a new hyperlink when you don't yet know where it'll link to: instead set the href to "#todo". This follows the //todo pattern recognised for unfinished code, and means you can now search your codebase for any links you forgot to finish off.

<a href="#">new link</a>
   becomes
<a href="#todo">new link</a>

eg: new link becomes new link

It will also give clues to any sharp-eyed testers / users that they should report a bug for you as the url will change to #todo when the unfinished link is clicked. It can often be seen in the status bar too.

This has the handy side-effect of avoiding the annoying jump to the top of the page that is the default behaviour when you click on a # link that's a placeholder.


For bonus points another little trick I like is to add a click handler with an alert to make it really obvious to any early users / testers that this is not done yet, and I've found this saves a lot of questions when you genuinely haven't finished, and also guarantees a quick bug report when you should have (not that I ever forget any of course :-D)

<a href="#">new link</a>
   becomes
<a href="#todo" onclick="alert('Not Implemented');">new link</a>

eg: new link becomes new link  <= click this to see the alert

Simple and effective.

If you agree, please help spread the word. Perhaps by retweeting my tweet



P.S. This goes hand in hand with a technique of picking points during development at which there should be no todo's left in your codebase with the exception of those with references to outstanding user story / bug numbers. I suggest before marking a user story as done, and at the end of each sprint as good points to review all todos in your codebase.

Further reading: