Eamonn Faherty

What Is A Stub

2016-07-01T00:00:00+00:00

Title: What is a stub? Date: 2016-07-01 23:39 Author: eamonnfaherty Category: testing Slug: what-is-a-stub Status: draft

I was recently at a python talk where there was a great presentation on testing. It covered the concepts of mocks, magic mocks and patches but it did not cover stubs. I found this omission interesting and then I looked through the python code at my place of work and realised that the python code I was looking at always tested using mocks and never used stubs.

Before I jump into the definition it is good to recap some of the basics:

The class you are testing is called the subject under test or sut
If your class works with in conjunction with other classes these are called collaborators
When you are testing your class you should replace non simple collaborators with test doubles

Mocks are a type of test double but they are not the only type. You can replace your collaborator with another type of test double - a stub.

Classic And London Style Tdd

2016-07-01T00:00:00+00:00

Title: Classic and London styles of TDD Date: 2016-07-01 23:39 Author: eamonnfaherty Category: testing Slug: classic-and-london-styles-of-tdd Status: draft

Within the TDD world there are at least two different schools:

the classic approach (defined by Kent Beck in Test Driven Development
the London approach (defined by Steve Freeman and Nat Pryce in Growing Object-Oriented Software Guided by Tests

The classic approach focuses on building from the bottom up. You start by defining smaller units in the regular red-green-refactor workflow whereas in the London style you define from the top down. You define what the system does as a whole and you replace parts as you develop them again in a red-green-refactor workflow.

The London approach is well suited to object oriented software as you start with a focus on the capabilities of a system. It is useful when you have a lot of confidence your requirements will not change - for example when you are working with a specification by example approach.

The classic approach is well suited to non object oriented software as you are focused on the effect

What Is An Api

2015-07-21T00:00:00+00:00

Title: What is an API? Date: 2015-07-21 12:38 Author: eamonnfaherty Category: product Tags: architecture, api Slug: what-is-an-api

Software systems are built to perform an action. For example, there are software systems that calculate tax, allow you to place an order or send an email.

It is very easy to think of software systems where the end user is a human. There is another type of user that exists - other software systems. For example, the software system that calculates tax may use another software system to discover the current rates of tax, the system that allows you to place an order may use another software system to get calculated delivery costs or the email system may use another software system to store address book / contact details - this is where APIs become very useful.

When a human user interacts with a software system they may view and click items on a webpage or within an application. They may even use their voice or perform a physical guesture to interact with the system. This is described as the graphical user interface (or GUI). Other software systems can also perform these actions using the same interface. However, these interactions have been designed to cater for human users. Software systems and human users are very different to each other. Software systems can communicate much more concisely and efficiently than human users can. Also, not all systems have need to cater for a human user.

API stands for application program interface. It is a way in which software systems send each other messages.

In the tax calculator example a human user would click the mouse cursor inside a form field and enter the salary, they would then enter their tax code and then eventually click submit. This is three interactions with the interface. If another software system wanted to communicate with the tax calculator it would send all the information and the instruction to perform the action in one interaction. This is much more concise and efficient.

So far I have identified the following concepts:

Interface - a way in which a user interacts with a system Graphical User Interface - a way in which a human user interacts with a system Application Program Interface - a way in which a software system interacts with another software system

There are many different styles of API in existance. Some are built on standards and consider more aspects that others. I will describing some of these in future blog posts so stay tuned for updates!

All Change Again

2015-07-21T00:00:00+00:00

Title: All change again!?!? Date: 2015-07-21 12:25 Author: eamonnfaherty Category: misc Slug: all-change-again

I am returning back to blogging! I have updated my site to use the awesome Pelican. My upcomming blog posts will be sharing my thoughts, opinions and experiences around the themes of development processes, architecture and tooling. I have a huge backlog of posts to write so without any more delays here goes!

Wordpress On Docker The Docker Way

2014-12-11T00:00:00+00:00

Title: Wordpress on docker (the docker way) Date: 2014-12-11 00:44 Author: eamonnfaherty Category: devops Slug: wordpress-on-docker-the-docker-way

I have just finished committing my initial version of Wordpress on Docker. It is available on github and available to download. I have followed the Docker best practices and have ensured that only one process runs per container. This was made possible using fig.

To use it all you need to do is clone the repo, add an entry to your hosts file pointing the name example to your docker service and run fig up. Once the process has finished running you can go to http://example to see your instance running.

I am welcoming pull requests should anyone feel like helping out. My todo list is roughly:

backup/restore of database
backup/restore of data container
have the static content served by nginx and not the php server
switch from php server to php-fpm - thus allowing better concurrency
remove index.php from the urls
decide what to do next

Fig Docker Wordpress

2014-12-11T00:00:00+00:00

Title: fig docker wordpress Date: 2014-12-11 10:04 Author: eamonnfaherty Category: devops Slug: fig-docker-wordpress

I have released a docker/fig combination allowing you to fire up a php, nginx and mysql containers with the latest version of wordpress preinstalled.

I have followed the docker best practices so everything:

runs in its own container
is configurable via the fig.yml file.

https://github.com/eamonnfaherty/fig-docker-wordpress

Startup X Under Nda

2014-12-09T00:00:00+00:00

Title: Startup X - Under NDA Date: 2014-12-09 11:19 Author: eamonnfaherty Category: projects Slug: startup-x-under-nda

Description of the Work

Startup X wanted to build an online labour marketplace. It was my role to understand the requirements, build data models and create a custom build django web app. The project is not fully live and so I cannot write about it. If you would like to know more about what I was doing please get in touch.

Key Responsibilities

Requirements analysis using UML
Data modelling using UML
Server provisioning using Fabric
Template integration
Backend programming using Django
Javascript programming
Stripe payment integration
LinkedIn API integration

Technical Solution

I used nginx, gunicorn, django to serve the application. I used postgres to store the application data. I used elasticsearch to power the search functionality on the site and I used the excellent sentry for exception monitoring.

Matching

Matching clients who want to pay for work to people who are willing and able to do the work is at the core of platform x. This was built using elasticsearch and custom python code. I made use of field and model boosts, as well as some custom logic written in python.

Currency

The currency of platform X is hours. Each hour has a purchase price, current price and a history of owners. This enables to the owner of platform X to calculate liabilities and to ensure price changes will not cause a loss of earnings. This was the most rewarding part of the project for me.

Project Dirt

2014-12-09T00:00:00+00:00

Title: Project Dirt Date: 2014-12-09 10:00 Author: eamonnfaherty Category: projects Slug: project-dirt

Description of the Work

Project Dirt had two existing social networking sites hosted on the Ning platform. It was my role to extract the data and migrate both of them to a custom build django web app. Static HTML templates were produced by a digital agency and it was up to me to write the python and javascript code to get the site up and running. During the project I had to build data models, prepare the server, write the backend python code and write the front end javascript code.

Key Responsibilities

Requirements analysis using UML
Data modelling using UML
Data migration using PHP and Python
Server provisioning using Fabric
Template integration
Backend programming using Django
Javascript programming

Technical Solution

I used nginx, gunicorn, django to serve the application. I used redis to store user session data and mysql to store the application data. I used celery as a task queue with redis as the broker. I used elasticsearch to power the search functionality on the site and I used the excellent sentry for exception monitoring.

Feeds

Within the Project Dirt platform as with most social networks you can be friends with people and you can follow them. Becoming a friend/follower means you subscribe to see updates on what they are doing within the platform on your feed. You can also visit their feed to see who they are following. I had to decide whether to have complex, expensive queries when you view a feed and have a simple update query when you become a friend or follower or to do the inverse. Given the frequency of feed views is far higher than the number of friendships/follows created I decided to have a complex, expensive async task to update feeds using celery instead so that when a feed is viewed it is a simple, cheap query.

Search

Search was a key feature for the Project Dirt platform. To create a great user experience it was imperative to be able to run searches quickly. I decided to use elasticsearch to gain this performance. We were able to deduce a lot of the searches on the site were people looking for others by name or by skill. To help these searches I decided to use the boost functionality from elasticsearch to alter the relevance of results and thus change the order in which they are returned. I also wrote custom search classes that returned snippets of where the results were found.

Upstream caching

Project Dirt have been featured in the media several times, appear at community events regularly and have a weekly email newsletter. These real life events cause a spike in traffic. The majority of the traffic in these situations are from users that are not logged in. To cope with the load I decided to use varnish cache as an upstream cache. I setup last modified and etag headers on the pages and used nginx to strip cookies so each non logged user sees the same page - as cached by varnish. This means users can view the pages within the server having to run any python code or contact the database. This strategy was planned from the start and so the models within the site were primed to help with the caching. This was the most rewarding part of the project for me.

Appsbooth

2014-12-09T00:00:00+00:00

Title: Appsbooth Date: 2014-12-09 11:47 Author: eamonnfaherty Category: projects Slug: appsbooth

Description of the Work

Appsbooth wants to reimagine the most popular sites on the Internet in such a way that they work together and provide a single user experience. These sites include Google Mail, Contacts, Calendar, AnyDo, eBay, CityMapper, Uber, AirBnB, and Park At My House.

It was my role to sift through the big picture to extract a product that could be built, marketed and used to bring in revenue.

After extensive requirements analysis achieved via interviews of the stakeholder and user research I drove the delivery towards building a “personal assistant in the cloud” as a first phase.

The concept was to create an application consisting of a Calendar, ToDo manager and Addressbook that worked together in harmony and allowed us to collect data. The application was to provide the user with a predictive user experience, driven by research I led into mental models and behavior analysis. Once there was enough data collected on the users we were going to mine the data to drive recommendations to sell goods and services through direct sales and affiliate channels.

Before starting the project I had to build prototypes/tests to prove the components of the application could work together and that we could mine the data.

I led the UX process. I identified the target audience of self-employed/independently contracting professionals aged 24 – 35 and conducted interviews to understand the lifestyle and their visual preferences. I explored the mental models and contexts building up some example scenarios for the user’s day to understand what we could predict and how could the application could be of assistance to them.

Once complete, I initiated the kick off of the feature with the rest of the team. I ran workshops where I presented initial versions of the feature through discussions, wireframes and conceptual models – explaining the user value and the business opportunity that it would bring.

I then worked with the visual designer providing prioritized lists of elements that had to be on screen at a given time. I continued to work with the visual designer throughout. Providing positive feedback and questioning design decisions on layout, input method choices and language – always drawing on the brand guidelines as a base.

I led on branding, hiring and managing external designers to explore ideas that we tested internally. I managed external designers supplying mood boards, brand guidelines and lo fidelity sketches.

Key Responsibilities

Requirements analysis using UML
Data modeling using UML
SOA architecture using Python and Docker
Server provisioning using Fabric and Docker
Template integration
Backend programming using Django
Javascript programming with AngularJS
Recruitment
Mentoring
Backlog management

Technical Solution

Backend

I built an initial proof of concept service oriented architecture. Each service was built using nginx, gunicorn, django and ran in a docker container. I used postgres databases for the services that needed a persistent layer and I used elasticsearch to power search. The provisioning and building of servers was fully automated using fabric and docker.

Frontend

I worked closely with the javascript developer who was tasked with the building of the frontend web and mobile applications using AngularJS. I guided him through building reusable components using hologram and creating automated builds and deploys for web and mobile applications.

Prototypes

I built the following prototypes:

Twilio – API integration creating accounts, provisioning mobile numbers, making calls and sending SMS.
Email scraping – API integration with gmail, outlook.com using OAUTH/IMAP to sync emails and plain IMAP for others
Addressbook scraping – API integration with gmail, outlook.com using OAUTH/IMAP to sync emails and plain IMAP for others
CARDDAV – API integration with gmail and outlook.com using OAUTH/IMAP
NLP – reading emails to understand their purpose

User Stories

2014-11-16T00:00:00+00:00

Title: User Stories Date: 2014-11-16 08:17 Author: eamonnfaherty Category: product Tags: agile, requirements Slug: user-stories

It may be hard to believe that in 2014 I still often get asked:

what is a user story?

I thought it might be beneficial to define it here so I can direct people to my blog for an answer and possibly a discussion instead of explaining several times (DRY principle).

To me, a user story is the smallest piece of business value that can be delivered as a piece of functionality. For example, an online room booking system for a hotel is not a user story as it comprises of many pieces of functionality; searching for rooms, checking availability, checking price, requesting the booking, seeing the booking status. Each of the pieces of functionality can be expressed as a user story following the three Cs framework from Ron Jeffries.

The three Cs framework encourages you to see user stories as:

Card - this is the summary of the user story. The card should be a reminder for a conversation and should follow the pattern:

As a USER I would like to DO SOMETHING so I CAN ACHIEVE SOMETHING

and should follow the INVEST principle:

Independent
Negotiable
Valuable
Estimable
Small
Testable
Conversation - this is the capturing of the discussions that occur or any special information that is needed to deliver the story. For example, when considering the searching for room availability there could be business rules that users can only perform 6 searches an hour etc. This is a way of specifying non functional requirements where a customer has been defined.
Confirmation - this is the acceptance criteria describing what needs to be true before the story can be considered delivered. It should describe every possible combination of scenario so the story can delivered catering for the normal course and every possible alternative course - that is when things go to plan and when things do not. For example, when considering searching for room availability there should be acceptance criteria for when there are rooms available and when there are no rooms available.

Following these best practices should stand you in a very good position where it is clearly defined what is going to be delivered. It is easy to fall out of this practice but during planning you should ensure these criteria are met to ensure everyone knows why they are doing this work, what the work entails and when the work is complete.

Elasticsearch Sentry Happy Days

2013-05-21T00:00:00+00:00

Title: elasticsearch + sentry = happy days Date: 2013-05-21 15:06 Author: eamonnfaherty Category: devops Tags: elasticsearch, sentry Slug: elasticsearch-sentry-happy-days

I have been using the amazing Sentry for quite some time and I love it. For anybody running a live site it really is a must!

I have also recently switched from xapian to elasticsearch as my search engine of choice.

BTW, I am on Ubuntu 12.04, installed elasticsearch via a deb file downloaded from their site and installed sentry via pip.

Once I was all setup I wanted to enabling logging of elasticsearch to my centralised sentry instance. This was a real pain and would have taken me a lot longer to complete (if at all) if it wasn’t for ColinHebert - details. Thanks again!

Here is what I had to do to get it working:
Elasticsearch uses log4j for logging but has a yaml file to configure it instead of a properties file. I had to append this to my /etc/elasticsearch/logging.yml file:

sentry: type: net.kencochrane.raven.log4j.SentryAppender dsn: "http://XXXX:YYY@myserver.com/N"

I also change the first line to read:
rootLogger: DEBUG, console, file, sentry

All I did was append sentry to the list of rootLoggers.

Once the config was sorted I had to download the dependencies:
raven-3.0-20130516.191912-9.jar
raven-log4j-3.0-20130516.191940-9.jar
commons-codec-1.8.jar
jackson-core-2.2.2-20130512.040915-3.jar
slf4j-api-1.7.5.jar

and add them to /usr/share/elasticsearch/lib on the machine hosting elasticsearch.

Once that was all done restarting elasticsearch was all that remained and I was logging to sentry!

Compiling Twitter Bootstrap On The Mac

2013-04-28T00:00:00+00:00

Title: Compiling twitter bootstrap on the mac Date: 2013-04-28 09:29 Author: eamonnfaherty Category: development Tags: bootstrap Slug: compiling-twitter-bootstrap-on-the-mac

Anybody who knows me in the real world has probably heard me rave about twitter bootstrap. I am not going to get into why it is a good framework or why frameworks are good in this post. If you would like hear stuff like that please contact me and I will see what I can do.

This post is about how to compile your very own copy of bootstrap! Why would you want to do that when the nice guys maintaining the package allow you to choose your own colour scheme? I am very grateful for the customise options but I wanted to be able to able to build the package myself for three reasons: 1) I am a geek and it is a geeky thing to do, 2) I wanted to be able to customise my theme and revisit it improving it as a I continue on my project (the customise page does not have a save/resume feature) and 3) I wanted to create a colour scheme that did not match the default - I didn’t just want to choose the colours and watch them cascade through the package. I wanted to change how the colours cascade through the package.

Without further delay this is what I did:
brew install node.js
You must have the excellent HomeBrew installed to run that command.

Once I had node.js installed it was a simple case of
cd twitter-bootstrap-src npm install make clean make bootstrap

This uses the excellent npm package manager to install the dependencies for bootstrap and then uses make to clean and build bootstrap. Once it completed you will have a working bootstrap installation in twitter-bootstrap-src/bootsrap.

I hope this helps and if you have any questions post a comment and I will try to help!

Ios App Signing

2013-01-26T00:00:00+00:00

Title: iOS App Signing Date: 2013-01-26 10:33 Author: eamonnfaherty Category: development Tags: iOS Slug: ios-app-signing

I have restarted my iOS development and thought how better to celebrate than writing a blog post.

iOS is the software that runs on the iPhone, iPod touch, iPad and AppleTV devices. It enables apps to be installed, removed, run etc. It also has some utility features such as battery monitoring and display etc.

In order for a developer to have an app they have written run on iOS it must be signed using a developer certificate issued by Apple. This signing means two things - all apps are developed by people have approved and every time you build an app is built the author of the app is verified using the certificate - so nobody can claim to be author of your app or author an app in your name.

The developer certificate is not the only thing used in the signing process. There is a provisioning profile file used. During development and testing apps are signed using a development provisioning profile. This profile lists the devices the app can be installed on. To add items to the list you must use Apples provisioning center. When you are ready to upload your app into the App Store you have to sign your app using your distribution profile.

Once you have a signed app you can install the app on your device using iTunes.

Project Dirt V2 Business Analyst Technical Architect Social Networking Consultant Developer

2013-01-25T00:00:00+00:00

Title: Project Dirt v2 - Business Analyst / Technical Architect / Social Networking Consultant / Social software engineering Date: 2013-01-25 15:55 Author: eamonnfaherty Category: projects Slug: project-dirt-v2-business-analyst-technical-architect-social-networking-consultant-developer

I was an agile, business value focused technical architect capturing requirements, creating solutions and helping improve business processes along the way.

I was responsible for all of the data modelling and the migration of two sites with over 5k users from an off the shelf (undocumented) Ning platform onto a bespoke Django build.

I established standards for documentation (using UML) and introduced a language the business owners used to describe their product to others - this was the business owners first development project. I introduced the concept of a backlog and held daily standups to ensure the business owners could track progress when desired.

I introduced game mechanics and social engagement circles to help increase user engagement and provided a solid platform for the business owners to continue on with. I created the ‘cluster’ feature they are using to earn revenue and I have provided suggestions of other features (at scrum story level) with revenue making suggestions.

I provisioned the whole stack - nginx, gunicorn, celery, mysql, redis, varnish-cache. I defined and implemented the caching policy - all not logged in users see the same rendered page so there are no db or django calls after the first page load until the page is edited. I wrote every line of python code the site used to go live using libraries like django-allauth, django-model-utils, django-dajax, easy-thumbnails, pybbm and django-celery.

Dti Game Design And Build Project

2012-11-25T00:00:00+00:00

Title: DTI - Game design and build project Date: 2012-11-25 15:55 Author: eamonnfaherty Category: projects Slug: dti-game-design-and-build-project

I worked with the campaign manager, consulting on their game design; helping with player motivations, player rewards and scoring mechanics.

I then went on to build the front end game and back end leader board.

My Caching Tales Part 1

2012-03-25T00:00:00+00:00

Title: My caching tales - part 1 Date: 2012-03-25 17:47 Author: eamonnfaherty Category: development Tags: caching, cdn, django, geo:lat=51.54171669999999, geo:lon=-0.08008210000002691, geotagged, London, nginx Slug: my-caching-tales-part-1

I am building a bespoke social network using Django. I am approaching the first release and I thought it would be a good time to look at the static asset performance. I installed yslow and tested my site. I got an F! Arghhh! Luckily, YSlow gives you a lot of guidance on how to improve your performance. I decided to write up what I did after @gmsharky asked me to explain a little more about what I was doing. BTW, after these steps I got to a grade C!

CDN usage

I moved all my static assets and media to dedicated subdomains so that the session and csrf cookies would not be transmitted whilst the assets were being requested. This was an easy win thanks to Djangos STATIC and MEDIA setup.

GZIP compression

I turned on gzip compression within nginx:

http { ... gzip on; gzip_http_version 1.1; gzip_vary on; gzip_comp_level 6; gzip_proxied any; gzip_types text/plain text/html text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript application/javascript text/x-js; gzip_buffers 16 8k; gzip_disable "MSIE [1-6].(?!.*SV1)"; ... }

I set far future expiration dates on my static content and disabled cookies for the urls:

server { listen 80; ... location ~* .(?:ico|gif|css|js|jpe?g|png)$ { access_log off; expires max; add_header Pragma public; add_header Cache-Control "public"; break; } ... }

JS and CSS minify

I used jezdez’s great django_compressor library to minify my js and css. This basically read my JS and CSS declarations and imported them into a single file for each. I had to tweak this due to possible name conflicts but it worked well in the end.

Next steps

The next thing for me to do is to use more sprite sheets instead of seperate images but there are not too many images anyway so I am going to stop for now.

In order to improve performance more I introduced varnish-cache to my stack. I had to do a lot of reading to come up with a working setup and will post that in another blog post coming soon - I need to finish my testing first!

Django Development Demystified Pt1

2012-02-10T00:00:00+00:00

Title: Django development demystified - Part 1 Date: 2012-02-10 11:45 Author: eamonnfaherty Category: development Slug: django-development-demystified-pt1

Django is an amazing development framework for those who want to separate concerns (write good, clean code) and want to get the job done - quickly!

It is written in Python and requires you to write Python code to use it. Python differs from PHP. PHP comes with most of the libraries you need out of the box and then has PEAR and PHAR to supply the rest. Python is a little more fragmented. With Python, you have to install the library and then install the python bindings, which is the python code that allows you to communicate with the libraries. For example, if you want to use mysql you must install mysql and then the mysql python bindings. This can be confusing and you can end up in a world of dependency nightmare!

With libraries like pip, vagrant and virtualenv and PaaS like dotCloud and Heroku I do not think it is such a pain anymore. These problems can now be solved once and shared across projects. For my own development (and sanity) I have put together a bootstrap vagrant file which allows me to build a virtual server. It using vagrant, which in turn uses VirtualBox, to build a virtual server and then uses Chef to install the recipes (which are individual dependencies). These recipeies include nginx, postgres etc. At the end of a couple of commands you end up with a working virtual server because somebody else has saved a working set for you. Great eh!?!

Here is my git repo. To use this all you need to do it install git and VirtualBox and then run the following commands in a terminal window:

[code lang=”bash” ]

git clone https://github.com/ineedarobot/geodjango-env

cd geodjango-env

vagrant up

[/code]

Once it is up you can login using vagrant ssh and your server is ready! Any questions please post a comment and I will try to help. If you spot any issues with my setup feel free to post an issue on the github repo.

BTW, this is actually a working setup for geodjango, meaning it installs Postgres, postgis and the gis libraries needed.

Python Mac Os X Mysql Problems

2011-06-21T00:00:00+00:00

Title: Python Mac OS X MySQL problems Date: 2011-06-21 06:14 Author: eamonnfaherty Category: development Tags: mac os x, mysql, python Slug: python-mac-os-x-mysql-problems

I recently had a three hour head banging off of wall session getting Python to play nicely with MySQL.

I was getting the following error:

File “/Library/Python/2.6/site-packages/Django-1.3-py2.6.egg/django/db/backends/mysql/base.py”, line 14, in raise ImproperlyConfigured("Error loading MySQLdb module: %s" % e) django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: dlopen(/Users/eamonnfaherty/.python-eggs/MySQL\_python-1.2.3-py2.6-macosx-10.6-universal.egg-tmp/\_mysql.so, 2): no suitable image found. Did find:

/Users/eamonnfaherty/.python-eggs/MySQL_python-1.2.3-py2.6-macosx-10.6-universal.egg-tmp/_mysql.so: mach-o, but wrong architecture

This was a complete mix up between 32bit and 64bit Python libraries working together with MySQL.

To fix it I put the following in my .profile file

export PATH=$PATH:/usr/local/mysql/bin

export CC=”gcc-4.0”
export CXX=”g++-4.0”

export PYTHONPATH=”/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/”
export DYLD_LIBRARY_PATH=/usr/local/mysql/lib/
export ARCHFLAGS=’-arch i386’
export VERSIONER_PYTHON_PREFER_32_BIT=yes

After adding this I ran a clean, build and install on the mysql-python library and everything worked! Phew!

Signals

2011-06-13T00:00:00+00:00

Title: Signals Date: 2011-06-13 15:53 Author: eamonnfaherty Category: development Tags: actionscript3, signals Slug: signals

Anyone that knows me offline has probably heard me singing the praises of signals.

I really like the stricter typing of signals compared to events. For me, strict typing means that my code is checked by the compiler (instantly, at compile time) as apposed to being checked by the AVM (eventually, at runtime). I have had countless times where I have seen code fail due to the event types declared in the handler method being wrong, even when the string values are stored as variables instead of using literals. The checking that event handlers are added correctly is not checkable by the compiler. This means we need to either blindly hope it all works out or rely on testing.

Signals (out of the box) fixes this issue but there is still another issue for me, the contract between an event (also a signal) and its handler. With events there are two contracts, the event type (the Event.type String) and the event data. Signals (out of the box) handles the event type issue by moving the name of the type into an interface as a signal, which is a great idea! The data problem is harder to solve.

There are two checks that should be performed on the data.

The first is validation. At the moment this is limited to type checking. When you set up a signal, you specify that the signal should be an int, String etc. I think this is a great start but I think there should be more (optional) validation checks available; range checks for ints and regex checks for Strings. When these validations fail then the signal should have a built in mechanism to throw an InvalidSignalError. This would tighten up the robustness of projects using signals and would definitely reduce the amount of code I write.

The second check is verification. This is a lot harder to check but is a much more valuable check to perform. I think this is up to developers to check when developing. I am currently using signals to send messages between objects. I like to keep the implementation of my objects hidden from others so when writing a class I am always mindful of what values are available to other objects. So, when writing a signal I often find myself doing the following:

[code lang=”as3” ]
public class ShowScreenSignal extends Signal
{
private static const MENU:int = 0;
private static const PLAY:int = 1;
…

public function ShowScreenSignal()
{
super(int);
}

public function dispatchMenu():void
{
dispatch(MENU);
}

public function dispatchPlay():void
{
dispatch(PLAY);
}

…

public function isMenu(message:int):Boolean
{
return message = MENU;
}

public function isPlay(message:int):Boolean
{
return message = PLAY;
}

…
}
[/code]

This means in my controller/mediator I call signal.dispatchPlay() and in my listener/command I check signal.isPlay(message) to check the message. This means nothing knows about the message values other than the signal. I can change the message to be a String without changing any of my controllers/mediators/command. This is better encapsulation. This works really well when using RobotLegs + Signals as you can subtype your command classes and have a condition in your execute method if (message.isPlay(message)).

This is solving one problem. I want to have one signal with many handlers based on the message. eg:

[code lang=”as3” ]
public class ShowPlayCommand extends SignalCommand
{
[Inject]
public var message:int;

[Inject]
public var signal:ShowScreenSignal;

override public function execute():void {

if (!signal.isPlay(message)) {
return;
}

//do something
}
}
[/code]

Facebook Graph Api Oauth Change

2011-06-08T00:00:00+00:00

Title: Facebook Graph API oauth change Date: 2011-06-08 17:37 Author: eamonnfaherty Category: development Tags: facebook, php Slug: facebook-graph-api-oauth-change

Facebook have changed their Graph API policy so that when you view a profile feed you need to have a valid oauth access token. See here.

Here is the PHP I used to get the feed of mypage.

[code lang=”php” ]
<?php

//config
$appId = “999”;
$appSecret = “I_LOVE_ROBOTS”;
$feedURL = “https://graph.facebook.com/mypage/feed”;
$limit = 10;

//script
$accessTokenUrl = “https://graph.facebook.com/oauth/access_token”;
$parameters = “client_id=$appId&client_secret=$appSecret&grant_type=client_credentials”;
$accessToken = file_get_contents($accessTokenUrl . “?” . $parameters);

$parameters = “$accessToken&limit=$limit”;
$result = file_get_contents($feedURL . “?” . $parameters);
?>
[/code]

Eamonn Faherty

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