The coding dojo at CodeMash 2012 was a blast this year. I ran two events in the dojo: a group exercise doing the Gilded Rose kata and the Ball Flow agile game. I thought the gilded rose kata we did as a group exercise was a great success. We had a good group of people, which was impressive considering that even with floor decals, people had trouble finding the coding dojo.

The coding dojo at codemash is a great place for actually doing things at CodeMash. If you’re tired of sitting there having someone talk at you, head to the coding dojo. It’s a place for writing code, learning, experimenting, and having a great time. We did katas, programming exercises, and some educational games in the dojo this year. If you did not make it to the dojo this year, we hope to see you next year!

Ball Flow

The Ball Flow game is an Agile exercise where a team of people work together in an experiment in self organization. The team will do some estimation, some planning, some retrospectives, and they will be trying to continually improve their process while aspects outside of their control continue to change. The team has to adapt and figure out how to keep working together effectively.

Object of the game:

Pass each of the 20 balls to each person in the group.

Rules of the game:

• A person may touch a ball more than once, but doing so isn’t ideal.
• Two people may not be touching the ball at the same time.
• You may not pass the ball to your nearest two neighbors
• If the ball touches walls (including floor and ceiling) or any furniture it must start over.
• The person who first picks up the ball must be the last to touch the ball.

What this group did

Our group started out by figuring that if they created an oblong shape, they could pass across pretty easily. They got in this shape and began passing around. They had two tall people stand back a step so that they could launch the ball over everyone else across the group. Their final pass went behind the backs of one side of the group back to the starting person who removed the ball from the game.

They spent some time planning and adjusting between each iteration. They made sure not to make big changes fearing the catastrophe that could occur. Each time they made modest improvements to their time.

As the game went on we added challenges, in one round we added a large number of pens that needed to be passed around as well.

In the final round we added in bags of potato chips, which were harder to throw across the room. Each time the group still managed to make slight adjustments to accommodate these changes and still slightly improve their times.

The CodeMash 2012 Ball Flow team was awesome! Great job everyone!

In software development, it is very important to continually learn and experiment with new techniques for building great software. Our job is to learn and improve the quality of code that we build over time. It is through this progression of experimentation, failing, succeeding, observing, reading, listening, and teaching that we as developers improve. In this post, I am going to discuss one way in which we as developers have learned something great and have taken it to the point of failure. This will allow us to learn, resolve, create new techniques, and succeed in the future.

What is Dependency Inversion?

One of the most important SOLID principles for testing our applications is the Dependency Inversion principle. I am very glad to see many more codebases using this technique as time goes on, however, I am seeing nearly as many others getting caught up in an easy mistake of using too much injection and putting interfaces on everything regardless of necessity. Lets start by defining dependency inversion so we’re all on the same page.

From Wikipedia:

In object-oriented programming, the dependency inversion principle refers to a specific form of decoupling where conventional dependency relationships established from high-level, policy-setting modules to low-level, dependency modules are inverted (i.e. reversed) for the purpose of rendering high-level modules independent of the low-level module implementation details. The principle states:

A. High-level modules should not depend on low-level modules. Both should depend on abstractions.

B. Abstractions should not depend upon details. Details should depend upon abstractions.

Reading directly from this, we can see that it says we should be depending on abstractions and in doing so we take a much lighter dependency. A dependency on an abstraction is not a big deal. A dependency on a concrete class is a big deal.

Is what I just said always true? No, it depends on the abstraction and the concrete class. For example, I make an exception for simple classes provided through the framework or language my code is primarily based on. For instance, I have no problem saying that my method depends on being given a DateTime object since there is no real gain by abstracting that object since that is a part of the framework and I will always be injecting in an object of that type.

When are interfaces and injection being overused?

One example of over-architected injection that I see a lot comes from something that I’ve taught many times when explaining SOLID. It’s the classic example of a dependency that people don’t realize they have.

DateTime.Today

I assume most of my readers know that this is a dependency taken directly on the system clock. It’s important to inject this dependency when your code behaves differently based on the value returned from that static method. When we extract that dependency, people have been taught (by many people including me) that a good way of testing this is to have some kind of IClock interface with an implementation of SystemClock accessing the computers clock by calling that static method we were just discussing.

Now when we write our method, we just give it a parameter of IClock. When we run our code in production, it’s taking in the SystemClock object, and in our tests we’re using a mock object. Great! We’ve reversed the dependency! Is that really what we wanted though? It might have been, but in some cases we could have just passed in the DateTime instance object returned from that method. This would have reduced complexity in our code.

Because we used this interface instead of just depending on simple concrete classes, we’ve actually made our code more difficult to use and maintain. Isn’t that the whole reason we were following SOLID in the first place? Yes, yes it is. This is of course a simple example, but you can find larger examples of where you could test your code and build in a nice structure without having to create pointless interfaces. Heck even in this example, you might have a good reason to need that Interface, but I am sure that you could get away with using it less. Every time you add that layer, you add complexity. Sometimes adding it is OK, because it gives you a much needed seam, but I doubt you need it as often as you think.

Please make sure that you need the interfaces and layers of abstraction before creating them. I’ve come across many codebases that become as complex or more simply by trying to do things “the right way”.

The road to software development hell is paved with good intentions.

Don’t like the way I phrased something? Think I overgeneralized? Did I make a mistake?

Call me out on it!

I appreciate the feedback.

I've been reading plenty of blog posts about Software Craftsmanship including a nice response by Uncle Bob. I ran a Software Craftsmanship precompiler workshop at CodeMash again this year, and I've even seen some good feedback and follow up from attendees. If you're in the area, I really recommend coming out to CodeMash next year. I am hoping to be there again next year doing the Software Craftsmanship precompiler.

Back in 2009, Steve Smith, Rich Henning, and I got together and discussed how we were going to create the Hudson Software Craftsmanship group. We figured out some times to meet and what types of exercises we would do. The group has had a steady group of attendees over this time period. We use a room that if we're prepared can fit about 30 people. Our usual group is between 15 and 25 people who show up ready to discuss software craftsmanship, values, principles, practices, unit testing, quality, and just about anything else. We get just enough people to have some really great discussions. Our next meeting is actually tonight and right now we have 28 people signed up for the event. We found some things to focus on and we did. We're all about lightning talks, discussions, and improving our coding abilities. 

In short, I've got Software Craftsmanship on the mind right now. I might as well spend some time discussing it.

I think Software Craftsmanship started as a good banner to rally behind in the fight to end crappy code. There are plenty of reasons why code might have been crappy, and I am all for rallying behind the banner of good, clean code. We're not talking about agile or lean when we talk about Software Craftsmanship, however, most craftsman are also supporting lean practices. In software craftsmanship we focus on the people, their relationships, and the code they write. I think in this sense, Software Craftsmanship can apply for any agile methods you use or even on a waterfall project. We're talking about writing code that fits the situation, which means in a lot of cases we need to cut down on the crap. We're more than that though. We're about making customers happy (sometimes the customers are just our bosses.) We are also trying to become better developers as a community. We need to help each other. The best developers in the world are the ones who have learned from other developers. You can never be great if you don't learn from others.

One of people's favorite terms to use is quality. It really has a meaning that is easy to define in generic terms, but is very difficult to nail down in terms if a quantity. I think we could all define quality in some way, but I think that we cannot determine the quality of code very well. It is very subjective, since people's definitions of quality and how they apply it are different. I think, however, that it is a central point in Software Craftsmanship. For that reason it is something that we should strive to understand and evaluate. If I were to give an important trait for a Software Craftsman to have it is the ability to determine and evaluate quality. Use whatever measure you like, but be able to understand quality and how to evaluate it depending on the circumstances of the code you're writing. Your definition of quality need not even match everyone else's. 

A topic that I've heard Steve Smith argue with people over plenty of times is whether or not a software craftsman should knowingly write low quality code. This usually comes up when the customer specifically wants you to write crap. The customer might even say that they'd rather have the product done sooner with bugs rather than have the code take any longer. I've heard some good arguments on both sides. To throw my two cents in, I'll just say that it really depends on the situation that you're evaluating.

I didn't have as good of a perspective on this topic until a great discussion on this very topic broke our during a HudsonSC meeting in which Joe Brinkman gave some very good arguments for why a software developer might not want to put extra time into code. His point was that for a startup, there is a better than average chance that you will be throwing the code away soon. You do not know if this code will ever be used again. It might be gone in a few months.

I admit in most situations I would argue for having higher quality code, but in the case of a startup I think there is good reason to write code fast and get something working. I think it is assumed for some startups that their code might have bugs or other issues. My interpretation of what Joe was saying is that the business might not even be a good one, so in those instances the software need only provide the basic functionality of the idea. If it is missing features or has some bugs you can still tell if the idea is something that the market is interested in. Startups have a completely different mindset. You need to quickly and cheaply find out if the business idea is going to work before your run out of funding. If I am interpreting him correctly he is basically talking about throw-away businesses not just throw-away apps. You keep starting and tossing businesses until one of them succeeds. I think in this situation, the code can reflect the business. Once the longevitiy of the business is determined, quality can be brought back into the mix.

To look at things from a different perspective, we can take the groups of people we have that attend HudsonSC who work at banks, insurance companies, and healthcare companies. All of these are long-standing businesses that need to maintain quality code at all times. It is these who have the traditional opinions on SoftwareCraftsmanship. These groups have no reason to lower quality. In fact if they don't maintain quality, they could have serious issues. I think most of us are in the boat where we expect the business we're working for to still exist in 6 months. This means that our code needs to survive and maintain for years after we first write it.

A software craftsman should know what customers want and be able to provide code which offers the value the customer is looking for. It is up to a craftsman to determine what solution is the best one for the job and be prepared to provide the highest quality code possible. In this instance I will say that the level of quality in the code is one that should be determined by the developer and the customer. 

After reading the title of this post, some people might be wondering why I am advocating commenting at all, because I’ve spoken out against commenting code before. My team and I were recently reading through some code that was littered with comments, and I do mean littered. There were tons, they were mostly useless statements like “//run”, and I swear there were more of them than actual code. This of course sparked some preaching to our choir about how comments in code are often less-than-useful. We of course settled on the time when they are useful being the XML comments on methods, but those should also only be used when writing public libraries where others will not have access to the source code or unit tests.

Comments on those methods are useful since tons of people will use the method and will not be able to see the guts of the method or examples of how to use it. This makes the comments useful. However, they need to be kept up-to-date (difficult task).

So what does all of this have to do with Listkov Substitution? Well, the principle basically says that all of the classes which implement an interface (or inherit) need to work the same way. There should be no difference between implementations as far as the calling code is concerned. In fact it is really about making sure that we maintain a consistent abstraction. If we say something about the interface it must hold true for the implementation. This means that any comments about the interface must hold true for every implementation.

We were wondering if the comments needed to be on each of the concrete classes or if we could just put it on the interface, and this was confirmed for me by Ben Heimann who quickly made an interface and a concrete class. Then he commented just the interface method and not the concrete one. We of course knew we would see the comment when using the interface, but we also saw it when we were dealing with the concrete class. Great work Visual Studio 2010! This means we don’t have to duplicate and also signals that we should follow LSP.

The concern is that if you have the comment in both places you would have to update them both. This also means that they could differ, and if they ever needed to intentionally differ then it means that we are violating LSP. Having the comment in the one place should at least point to the fact that we should maintain the same behavior for the calling code in all implementations of our interfaces.

Over a year ago, Steve Smith, Rich Henning, and I met to plan our first meeting of the Hudson Software Craftsmanship group. We decided on a format for the group, planned how we were going to organize the events, and came up with some topics to discuss for our first meeting since we didn’t expect people to arrive for the first meeting with lightning talks and discussion topics prepared. We also came up with the time for the meeting which would be the third Wednesday of each month, and we set up the first meeting of the group.

Since that point we have been very impressed with the core group of members who have stepped up to take part in the group and really help improve their own and others’ craft. We put on a local Software Engineering 101 event in Cleveland where four HudsonSC members, @ardalis, @brendoneus, @kevinkuebler, and @ropog, took the time to discuss some topics and run the group in exercising their skills. The class was a great success and I, as a member of HudsonSC was proud to be a part of it.

The group is always looking for new members, so if you’re in the Northeast Ohio area, please drive to Hudson, Ohio once a month on the third Wednesday of the month. We prefer if you sign up, but you can just show up and we will not turn you away. Everyone is welcome.

Sign up for the August 2010 event now!

Look for more information on the group on the Hudson Software Craftsmanship site.

Fresh opinions, ideas, and technology are always welcome.

Thank you for a great year, HudsonSC!

Interfaces and base classes allow us a great deal of power in object oriented programming. We are able to accept a base type or interface and be given an implementation or an inheritor and continue working correctly. What if, however, we need to be able to accept more than one type, which have the same methods or properties, but to not share an interface or base class? Often the best answer is to add a common interface to these, so that the shared behavior is defined. In most of my cases when I need to do something like this, it is because I don’t have the source code for one or more of the classes.

Our answer in this case is the dynamic types which we added in to C# 4.0. In this new revision of the language, we are able to declare an object deferring its type until runtime. We will define how we will use the object now, and at runtime our code will attempt to use that object.

The following is some example code showing how to use the dynamic keyword to use two classes interchangeably:

class Program
{
    public static List<DateTime> 
        Dates = new List<DateTime>();

    static void Main(string[] args)
    {
        var someClass = new SomeClass(DateTime.Now);
        GetEventDate(someClass);
        var otherClass = new OtherClass(DateTime.Now);
        GetEventDate(otherClass);

        var values = Dates.Select(d => d.ToShortDateString());
        Console.WriteLine(string.Join("---", values));
    }

    private static void GetEventDate(dynamic objectWithDate)
    {
        Dates.Add(objectWithDate.Date);
    }
}

public class SomeClass
{
    public DateTime Date { get; set; }

    public SomeClass(DateTime date)
    {
        Date = date;
    }
}

public class OtherClass
{
    public DateTime Date { get; set; }

    public OtherClass(DateTime date)
    {
        Date = date;
    }
}

So in this example, if we say that I didn’t have access to OtherClass in order to give it some interface, using the dynamic would allow me to get around this and use a convention-based approach to development. When the alternative is some cluttered approach, I am always in favor of simplifying the readability and usability of my source code. Now there is less of a reason to complain that a certain class from a library or generated code doesn’t implement an interface. (There is still reason, but at least we can avoid some of the issues at play.)

Now that the dust has settled from the recent Software Engineering 101 event we put on in Cleveland, I figured I would repost some of the material I talked about. This means some of connections that I vocalized and supplement the material from the slides I used for Software Engineering 101.

Object Oriented Principles, Practices, and Patterns

My first talk of the day was on Object Oriented Principles, Practices, and Patterns in which I start by discussing some common principles of object oriented programming: abstraction, encapsulation, inheritance, polymorphism, and I added composition in for good measure, which of course isn’t on its own a principle, but I feel deserves to be mentioned as its own entity at that point.

I covered an assortment of good practices for software developers to follow. Since Steve Smith was following my talk with one on SOLID, so I didn’t take the opportunity to discuss the Open/Closed Principle, which states that your code should be open to extension and closed to modification. This means that you can add to the behavior of your code by adding new code and not modifying what you already have.

In my patterns section I covered two of my favorite design patterns: the Strategy Pattern and the Template Method Pattern. These two are great for discussing with people. They’re very similar yet very different; one encapsulates the structure of an algorithm and allows for modification of the details of the steps while the other focuses on allowing for different algorithms to be used interchangeably. Each uses polymorphism, abstraction, encapsulation, and inheritance. They’re simple to explain and demonstrate, and they’re also very powerful. This makes them great examples.

Combining Everything

When we combine these principles and some design patterns we can achieve some great things. The strategy pattern is one of my favorite patterns, because it is very useful and improves maintainability greatly. I use it often. It uses, abstraction, encapsulation, composition, polymorphism, and either inheritance or interface implementation. On top of that it also helps follow the Open/Closed Principle, increasing the ease for changing the behavior of an application when the requirements change.

In my talk I was asked a great question, “if I don’t know design patterns, how will I know what I don’t know.” In other words, how can you possibly select the correct design problem to solve a problem. I recommended reading learning plenty just so you’ll be more prepared. There are plenty of books, and you don’t always need “the best” solution. Usually a good solution to the problem is enough. Steve Smith chimed in with a great answer though, he suggested practicing coding katas, which will often solve problems using design patterns or at least good, worthwhile practices.

Steve Smith tagged me with his books post last week, which was his response to Sadukie’s post on books. I will of course keep this modern chain letter going. Here be dragons books.

Currently and just finished reading:  I just visited my local library and picked up a copy of Planet of Twilight, which is the third book in a Star Wars trilogy. I’ve recently finished reading the second book of the same trilogy, Darksaber. Although I don’t like the name “Darksaber,” it is a well-written, entertaining book. My wife tells me, however, that I will not find the same to be true of Planet of Twilight.

On the technical side of things I’ve just started reading Agile Principles, Patterns, and Practices in C#, which lines up very well with a lot of the techniques I use in my day-to-day development, and I will be adding it to my required reading list shortly.

I plan to be reading a little bit less right now as I have been playing StarCraft 2. Let me know if you want to play a match.

From what medium I like my books: I haven’t ever gotten any of the digital readers, but I have read PDFs on my computer and on my phone. I’ve also used some of the book reader applications for my phone, and I tend to prefer reading books on pages printed on dead trees. Perhaps it’s just that I’ve not yet tried a good enough interface for digital reading. I intend to try one eventually.

Some book recommendations: If you’re interested in reading any Star Wars novels I would recommend that you begin with either the Thrawn trilogy by Timothy Zhan: Heir to the Empire, Dark Force Rising, and The Last Command or with the Michael Stackpole’s X-wing series: Rogue Squadron, Wedge's Gamble, The Krytos Trap, and The Bacta War.

If you’re interested in reading some fantasy stories I would recommend starting the Drizzt books starting with the first trilogy written about him, The Icewind Dale trilogy: The Crystal Shard, Streams of Silver, and The Halfling's Gem.

For technical books, please check my not-so-up-to-date list of recommended software development books.

Tag, You're Up Next...

What are you reading?

Scott Forsyth

Ben Heimann

Andy Vanek

Jeffrey Palermo

Chris Wagner

This week I’ll be speaking at a free day-long event for developers to improve their software engineering skills. The event is being held at the Microsoft office in Independence, Ohio. Microsoft is hosting the event being organized by the Hudson Software Craftsmanship group and NimblePros consulting services.

I’ll be kicking off the event with my main topic: Principles of Object Oriented Programming. Other topics will include: SOLID Software Development, Software Testing, and Specification Driven Testing. In the afternoon we’ll be doing Hands-On Exercises.

There are only a dozen seats remaining for the event scheduled for July 16, 2010. We’ll be starting in the morning at 8:30 AM and running until 4:00 PM. We’re looking forward to seeing you there!

Registration for the event is free and easy. Sign up now for the Software Engineering 101 – Cleveland event. Seats are limited, so register soon.

Earlier this week, the second iteration of this developer-targeted online challenge was released. The Toughest Developer Puzzle Ever started last year, and you can do either of the puzzles. I recommend tackling TDPE 2 if you haven’t done either one yet. There will be prizes sent out to the first 100 people to finish the puzzle, so get solving! Very few people have solved the puzzle so far.

TDPE Classic was created mostly by Jeff Blankenburg with assistance from Sarah Dutkiewicz and me. The puzzle ended up being 30 levels, and I it was a challenging set of puzzles. It was great fun working on it, and solving the puzzles was also a blast.

This year, we kicked things up a notch. We made harder puzzles, we made more puzzles, and we got extra help working on them. If you were looking for a challenge, I think we have a good one this year.

This years puzzle making team includes:

• Jeff Blankenburg
• Sarah Dutkiewicz 
• Brendan Enrick 
• Charles Hawley 
• Clint Edmonson 
• Justin Kohnen 
• Steve Smith 
• Dave Swersky 
• Josh Holmes

And to help you on your way I’ll give you some advice.

• Don’t believe everything you see in the puzzle.
• A puzzle may seem tedious even when it isn’t.
• There may be more than one way to solve a puzzle.
• Find all available clues, not just the obvious ones.
• Use your head.

I hope you enjoy the puzzle! Good luck!