Evolvability of Code: Uniform Access Principle

Most programmers like freedom. So there are many means of hiding implementations in modern programming languages, e.g. interfaces in Java, header files in C/C++ and visibility modifiers like private and protected in most object-oriented languages. Even your ordinary functions or public class interface gives you the freedom to change the implementation without needing to touch the clients. Evolvability in this sense means you can change and refine your implementations without requiring others, namely clients of your code, to change.

Changing the class interface or function signatures within a project is often possible and feasible, at least if you have access to all client code and use powerful refactoring tools. If you published your code as a library or do not want to break all client code or forcing them to adapt to your changes you have to consider your interface code to be fixed. This takes away some of your precious freedom. So you have to design your interfaces carefully with evolability in mind.

Some programming languages implement the uniform access principle (UAP) that eases evolvability in that it allows you to migrate from public attributes to properties/method calls without changing the clients: Read and write access to the attribute uses the same syntax as invoking corresponding methods. For clarification an example in Python where you may start with a class like:

class Person(object):
  def __init__(self, name, age):
    self.name = name
    self.age = age

Using the above class is trivial as follows

>>> pete = Person("pete", 32)
>>> print pete.age
# a year has passed
>>> pete.age = 33
>>> print pete.age

Now if the age is not a plain value anymore but needs checking, like always being greater zero or is calculated based on some calendar you can turn it to a property like so:

class Person(object):
  def __init__(self, name, age):
    self.name = name
    self._age = age

  def age(self):
    return self._age

  def age(self, new_age):
    if new_age < 0:
      raise ValueError("Age under 0 is not possible")
    self._age = new_age

Now the nice thing is: The above client code still works without changes!

Scala uses a similar and quite concise mechanism for implementing the UAP wheres .NET provides some special syntax for properties but still migration from public fields easily possible.

So in languages supporting the UAP you can start really simple with public attributes holding the plain value without worrying about some potential future. If you later need more sophisticated stuff like caching, computation of the value, validation or even remote retrieval you can add it using language features without touching or bothering clients.

Unfortunately some powerful and widespread languages like Java and C++ lack support for UAP. Changing a public field to a more complex property means the introduction of getter and setter methods and changing all clients. Therefore you see, especially in Java, many data classes littered with trivial getter and setter pairs doing nothing interesting and introducing unnecessary bloat to maintain the evolvability of the code.

Summary of the Schneide Dev Brunch at 2012-05-27

If you couldn’t attend the Schneide Dev Brunch in May 2012, here are the main topics we discussed neatly summarized.

Yesterday, we held another Schneide Dev Brunch on our roofgarden. The Dev Brunch is a regular brunch on a sunday, only that all attendees want to talk about software development and various other topics. If you bring a software-related topic along with your food, everyone has something to share.

We had to do another introductory round because there were new participants with new and very interesting topics. This brunch was very well attended and rich in information. Let’s have a look at the main topics we discussed:

Agile wording (especially SCRUM)

This was just a quick overview over the common agile vocabulary and what ordinary people associate with them. A few examples are “scrum“, “sprint” and “master”. We agreed that some terms are flawed without deeper knowledge about the context in agile.

Book: “Please Understand Me”

if you are interested in the Myers-Briggs classification of personality types (keywords: are you INTJ, ESTP or INFP?), this is the book to go. It uses a variation of the personality test to classify and explain yourself, your motives and personal traits. And if you happen to know about the personality type of somebody else, it might open your eyes to the miscommunication that will likely occur sooner or later. Just don’t go overboard with it, it’s just a model about the most apparent personality characteristics. The german translation of the book is called “Versteh mich bitte” and has some flaws with typing and layouting errors. If you can overlook them, it might be the missing piece of insight (or empathy) you need to get through to somebody you know.

TV series: “Dollhouse”

As most of us are science fiction buffs and hold a special place in our heart for the series “Firefly”, the TV series “Dollhouse” by Joss Whedon should be a no-brainer to be interested in. This time, it lasted two seasons and brings up numerous important questions about programmability every software developer should have a personal answer for. Just a recommendation if you want to adopt another series with limited episode count.

Wolfpack Programming

A new concept of collaborative programming is “wolfpack programming” (refer to pages 21-26). It depends on a shared (web-based) editor that several developers use at once to develop code for the same tasks. The idea is that the team organizes itself like a pack of wolves hunting deer. Some alpha wolves lead groups of developers to a specific task and the hunt begins. Some wolves/developers are running/programming while the others supervise the situation and get involved when convenient. The whole code is “huntable”, so it sounds like a very chaotic experience. There are some tools and reports of experiments with wolfpack programming in Smalltalk. An interesting idea and maybe the next step beyond pair programming. Some more information about the editor can be found on their homepage and in this paper.

Book: “Durchstarten mit Scala”

Sorry for the german title, but the book in this review is a german introductory book about Scala. It’s not very big (around 200 pages) but covers a lot of topics in short, with a list of links and reading recommendations for deeper coverage. If you are a german developer and used to a modern object-oriented language, this book will keep its promise to kickstart you with Scala. Everything can be read and understood easily, with only a few topics that are more challenging than there are pages for them in the book. The topics range from build to test and other additional frameworks and tools, not just core Scala. This book got a recommendation for being concise, profound and understandable (as long as you can understand german).

Free Worktime Rule

This was a short report about employers that pay their developers a fixed salary, but don’t define the workload that should happen in return. Neither the work time nor the work content is specified or bounded. While this sounds great in the first place (two hours of work a week with full pay, anybody?), we came to the conclusion that peer pressure and intrinsic motivation will likely create a dangerous environment for eager developers. Most of us developers really want to work and need boundaries to not burn out in a short time. But an interesting thought nevertheless.

Experimental Eclipse Plugin: “Code_Readability”

This was the highlight of the Dev Brunch. One attendee presented his (early stage) plugin for Eclipse to reformat source code in a naturally readable manner. The effect is intriguing and very promising. We voted vehemently for early publication of the source code on github (or whatever hosting platform seems suitable). If the plugin is available, we will provide you with a link. The plugin has a tradition in the “Three refactorings to grace” article of the last Dev Brunch.

Light Table IDE

A short description of the new IDE concept named “Light Table”. While the idea itself isn’t new at all, the implementation is very inspirational. In short, Lighttable lets you program code and evaluates it on the fly, creating a full feedback loop in milliseconds. The effects on your programming habits are… well, see and try it for yourself, it’s definitely worth a look.

Inventing on Principles

Light Table and other cool projects are closely linked to Bret Victor, the speaker in the mind-blowing talk “Inventing on Principles”. While the talk is nearly an hour of playtime, you won’t regret listening. The first half of the talk is devoted to several demo projects Bret made to illustrate his way of solving problems and building things. They are worth a talk alone. But in the second half of the talk, Bret explains the philosophy behind his motivation and approach. He provides several examples of people who had a mission and kept implementing it. This is very valuable and inspiring stuff, it kept most of us on the edge of our seats in awe. Don’t miss this talk!

Albatros book page reminder (and Leselotte)

If you didn’t upgrade your reading experience to e-book readers yet, you might want to look at these little feature upgrades for conventional books. The Albatros bookmark is a page remembering indexer that updates itself without your intervention. We could test it on a book and it works. You might want to consider it especially for your travelling literature. This brought us to another feature that classic dead wood books are lacking: the self-sustained positioning. And there’s a solution, too: The “Leselotte” is a german implementation of the bean bag concept for a flexible book stand. It got a recommendation by an attendee, too.


If you ever wondered what you just read: It might have been bullshit. To test a text on its content of empty phrases, filler and hot air, you can use the blabla-meter for german or english text. Just don’t make the mistake to examine the last apidoc comments you hopefully have written. It might crush your already little motivation to write another one.

Review on Soplets

In one of the last talks on the Java User Group Karlsruhe, there was a presentation of “Soplets”, a new concept to program in Java. One of our attendees summarized the talk and the concept for us. You might want to check out Soplets on your own, but we weren’t convinced of the approach. There are many practical problems with the solution that aren’t addressed yet.

Review on TDD code camp

One of our attendees lead a code camp with students, targeting Test Driven Development as the basic ruleset for programming. The camp rules closely resembled the rules of Code Retreats by Corey Haines and had Conway’s Game of Life as the programming task, too. With only rudimentary knowledge about TDD and Test First, the students only needed four iterations to come up with really surprising and successful approaches. It was a great experience, but showed clearly how traditional approaches like “structured object-oriented analysis” stands in the way of TDD. Example: Before any test was written to help guide the way, most students decided on the complete type structure of the software and didn’t aberrate from this decision even when the tests told them to.

Report of Grails meetup

Earlier last week, the first informal Grails User Group Karlsruhe meeting was held. It started on a hot late evening some distance out of town in a nice restaurant. The founding members got to know each other and exchanged basic information about their settings. The next meeting is planned with presentations. We are looking forward to what this promising user group will become.


This Dev Brunch was a lot of fun and new information and inspiration. As always, it had a lot more content than listed here, this summary is just a best-of. We are looking forward to the next Dev Brunch at the Softwareschneiderei. And as always, we are open for guests and future regulars. Just drop us a notice and we’ll invite you over next time.

Open Source Love Day October 2010

Our Open Source Love Day for October 2010 brought love for the cmake hudson plugin. Other issues were addressed but not finished. If you like to type fast and accurate, we suggest you check out typeracer.

On Friday two weeks ago, we held our Open Source Love Day for October 2010. This day was special in several ways. We strayed very far from the usual schedule for this day, there were several internal tasks that couldn’t be delayed and we introduced a “fun practice” event. But we eventually produced something valuable this day.

The Open Source Love Day

We introduced a monthly Open Source Love Day (OSLD) to show our appreciation to the Open Source software ecosystem and to donate back. We heavily rely on Open Source software for our projects. We would be honored if you find our contributions useful. Check out our first OSLD blog posting for details on the event itself.

The distractions

  • A regular project needed an urgent cost estimation by the whole team. This was the last opportunity because of an upcoming parental leave to have the team together for a long time.
  • Another regular project needed an urgent problem solved. This turned out to be so obscure that one of our developers had to be on-site. You can read about it in this blog entry now.
  • We received several shipments of office furniture and computer parts. They had to be checked and placed in.
  • We had a fun practice event. We discovered the online “game” typeracer and practiced our raw typing skill against each other for some time. Pro tip for beginners: don’t look at the highscores!

On this OSLD, we accomplished the following tasks:

  • A new version 1.8 of the cmakebuilder hudson plugin implements several feature requests. You can now choose to NOT clean your workspace before building and set different paths for the cmake installation for every job or node (hudson slaves). The latter option can be applied using an environment variable.

On this OSLD, we also tried the following tasks:

  • We keep an eye on Scala and its associated web framework Lift as a promising technology. One issue with Lift that bugs us is the use of “sun bastard format” properties for internationalization. We tried to teach Lift to accept UTF-8 encoded property files. After a lot of “downloading the internet” (you can always tell which project uses maven by their initial setup delay), we quickly implemented our own ResourceBundle.Control. But the Lift framework itself could not be built: “Error occurred during initialization of VM: Could not reserve enough space for object heap”. We ran out of time and will investigate in this issue on the next OSLD.
  • Grails is another web framework we use in projects. There are some bugs that really annoy us, and the OSLD is the perfect time to fix them. One of these bugs is GRAILS-6475, which we tried to reproduce with the latest code base. After writing a test case that would go green unexpectedly, we tried to provoke the error by setting up a sample project. The bug didn’t show up there, too. We left a comment in the issuetracker and ceased development.

What were our lessons learnt today?

  • You can’t tear off massive amounts of time from the OSLD and expect it to still be working. An OSLD doesn’t scale down apparently.
  • Most issues that can’t be done fail with the project’s build. The build process of a foreign project is the most crucial phase in your decision on commitment. If it fails, your participation in the project is at risk. We’ve seen many brittle, undocumented and incredible complex build processes now. And we can state one thing: It doesn’t stop with throwing maven at a project, you still have to “think the build”.

Retrospective of the OSLD

This OSLD was special in the amount of non-OSLD work done. The remaining efforts weren’t as successful as we wished. This has been an ongoing issue with our OSLD for the last months now and we are looking forward to adapt our workstyle to yield better results in the future. The distraction by typeracer was fun, though.

Follow-up to our Dev Brunch March 2010

A follow-up to our March 2010 Dev Brunch, summarizing the talks and providing bonus material.

Yesterday we held our Dev Brunch for this month. It was the second brunch in our new office, with some attendees visiting it for the first time. The reactions were the same: “I want to move in here!”. The topics were of different kinds, from live presentations to mere questions open for discussion.

The Dev Brunch

If you want to know more about the meaning of the term “Dev Brunch” or how we implement it, have a look at the follow-up posting of the brunch in October 2009. We continued to allow presence over topics. These topics were discussed today:

  • Singleton vs. Monostate – We all know that Singletons are bad for your test coverage, they make a poor performance on your dependency chart and are generally seen as “evil”. We discussed the Monostate pattern and if it could solve some of the problems Singletons inherently bring along. Based upon the article from Uncle Bob, we concluded that Monostates are difficile at least and don’t help with the abovementioned problems.
  • What is “agile” for you? – This simple question provoked a lot of thoughts. You can always obey the Agile Manifesto word by word without understanding what the deeper motives are. The answer that fitted best was: “You can name it when you see it”. We concluded that it’s easy and common practice to label any given process “agile” just to sound modern.
  • News around Yoxos – If you are using Eclipse, you’ve certainly heard about Yoxos already. Now during the EclipseCon 2010, good news were announced. We got a sneak peek on the new Yoxos Launcher and how it will help in managing your pack of Eclipse installations. We are looking forward to become beta testers because we can’t wait to use it.
  • Teaser talk for “Actors in Scala” – The actor paradigm for parallel programming is a promising alternative to threads. While threads are inevitable complex even for simple tasks, actors seem to recreate  a more natural approach to parallelism. This talk was only the teaser for a more in-depth talk next time, with hands-on code examples.
  • Properties in Scala – This talk had lots of code examples and hands-on discussion about the Properties feature of Scala. Properties are an elegant way to reduce your boilerplate code for simple objects and to sustain compatibility with Java frameworks that rely on the Java Beans semantics. We clearly understood the advantages, but ran into some strangeness related to the conjoint namespaces of fields and methods along the way. Scala isn’t Java, that’s for sure.
  • Introduction to PreziPrezi is a modern presentation tool in the tradition of the dreaded PowerPoint or Apple’s Keynote. It adds a twist to your presentation by adding two new dimensions: laying out everything on a big single canvas (no slides!) and relying heavily on zooming effects. The online editor is surprisingly usable, yet simple and lightweight. If you want to meet prezi, check out the introduction prezis and the showcase on their homepage.

As usual, the topics ranged from first-hand experiences to literature research. For additional information, check out the comment sections. Comments and resources might be in german language.

Retrospection of the brunch

We keep getting better in timing our talks. We nearly maintained our time limit and didn’t hurry anything. For the next brunch, we are looking forward to use our new office roof garden to brunch and talk in the springtime sun.

Follow-up to our Dev Brunch February 2010

A follow-up to our February 2010 Dev Brunch, summarizing the talks and providing bonus material.

Today, we held our second Dev Brunch for 2010. It was the first one in the new office, with some packing cases still around. The brunch had some interesting topics, most of them small and focussed. We discussed if the topics should be announced beforehands to avoid collision, but defined these collisions as enrichments rather than duplications.

The Dev Brunch

If you want to know more about the meaning of the term “Dev Brunch” or how we implement it, have a look at the follow-up posting of the brunch in October 2009. This time, we didn’t urge all participants to bring their own topic. Presence is more important than topic.

  • Scrum adventure book review – There are lots of book on the Scrum project management process. But the one called “Geschichten vom Scrum” (sorry, it’s a german book!) will teach you all the basics and some advanced practical topics of Scrum while telling you the fairy tale of a kingdom haunted by dragons. By following a group of common fairy tale characters in their quest to build a dragon trap the Scrum way, you’ll learn a great share of real world Scrum and still be entertained. You might compare this book to Tom DeMarco’s “The Deadline”, a novel about general project management.
  • What is the Google Web Toolkit? – Based on the learning from the presentation of the Karlsruhe Java User Group (JUG-KA), we skipped through the slides to get to know the Google Web Toolkit (GWT) framework. Advanced topics were discussed in the next talk.
  • First hand experience with GWT – We talked about the sweet spots and pain points of Google Web Toolkit, based on the experiences in a real project. This was very helpful to sort out the marketing promises from the definite advantages. While the browser doesn’t affect the developer anymore, the separation of client (browser) and server will still leak through.
  • First impressions of the Lift framework – The way to go with web application development in Scala is Lift. It’s a framework borrowing the best from “Seaside, Rails, Django and Wicket” and combining it with Scala and the whole Java ecosystem. While this talk was just a teaser, it already looked promising.

As usual, the topics ranged from first-hand experiences to literature research or summaries of recently attended presentations. You can check out the comments for additional resources, but they may be in german language.

Retrospection of the brunch

It’s right to grant access to “non-topics”. This will lower the barrier for occasional guests while they are valuable for their experiences and insights. This brunch was enriched by yet another topic collision, which is the perfect situation for a more in-depth discussion.

Follow-up to our Dev Brunch January 2010

A follow-up to our January 2010 Dev Brunch, summarizing the talks and providing bonus material.

Today was our first Dev Brunch for the new year 2010. We held a well-attended and very interesting session with lots of coffee. It was the last brunch in the old office, as we are currently moving to new rooms. The brunch ended with a sneak peek into the new office.

The Dev Brunch

If you want to know more about the meaning of the term “Dev Brunch” or how we realize it, have a look at the follow-up posting of the brunch in October 2009. We used notebooks throughout the sessions today.

The topics of this session were:

  • Agile done wrong – A project that was converted to be agile now tends to be even more conservative when management lost faith in their developers. A rather sad first-hand story, with lots of Dilbert-style humor in it.
  • Implicits in Scala – Scala introduces a powerful feature of implicit (hence the name) type conversion that can be used to greatly simplify work with complex type systems. Or to totally disturb your understanding of it.
  • Follow-up on the local XP-Days – The XP Days Germany of andrena objects ag are a small, yet powerful conference in Karlsruhe. We got a summary of the overall style and different presentations. Things like Pokens, Pecha Kucha (watch your pronunciation of it) and live code katas are all very promising stuff. Most presentation content itself was interesting, too.
  • Exception safety in Java – A classical topic of (not only) C++, ported to Java. This overview presentation highlighted the basics of exception safety and some insights for Java, mostly borrowed from Alan Griffiths.
  • Preview of an Eclipse based product – We won’t go into much detail here, but we got a glance of an upcoming product that will greatly ease the use of multi-site programming with Eclipse. The EclipseCon 2010 in March might get promising.

The topics ranged from first-hand experiences to literature research. We look forward to provide additional information linked in comments on this article, partially in german language.

Retrospection of the brunch

It was very entertaining to meet everyone after the long holiday season. Lots of news and chatter and stuff. The topics were interesting and thought provoking. If you weren’t there, you’ve missed something. Check out the comments for compensation.