I was in the middle of a TDD coaching session a couple of days ago when it hit me - people need a tool that will help them write one assert at a time!

So I started looking for one, and after about 2 exhausting minutes of trying to Google it, I gave up and wrote one myself.

Give it a try at http://www.rauchy.net/oapt.

Following my post on the Special Case pattern, I just wanted to give a few more examples in which the pattern proves to be really helpful. In the previous post, we talked about using the Special Case pattern when returning collections, but you can use it in other places as well.

Subclassing

Suppose we have a cached collection of User objects, and we want to fetch a specific User and save it to the database.

User user = cache.Get(”John”);
if (user != null)
{
     user.Save();
}

If we subclass User with a class called MissingUser, and have our cache object return it when it can’t find a user, we can reduce our calling code to:

User user = cache.Get(”John”);
user.Save(); 

MissingUser.Save() overrides User.Save() and does nothing.

Side note: we could definitely go with checking cache.Contains(”John”), and acting on the result, but I think this is too much detail for this level of abstraction, and may be violating Tell, Don’t Ask.

Instantiation

Suppose we want to display a User’s profile. Our User class has a string called Name and a bitmap called Picture.

User user = profiles.Get(”Mark”);
if (user != null)
{
     this.Name = user.Name; // Binding is for the weak.
     this.Picture = user.Picture;
}

When a User is not found in the profiles repository, we could make it return an instance of the regular User class, where User.Name = “Not Found”, and Picture is something like

This way, we can just write:

User user = profiles.Get(”Mark”);
this.Name = user.Name;
this.Picture = user.Picture;

and a profile will always be displayed.

Conditioning on Instantiation

What if we wanted to check if a User exists in a managers repository, and only if it is not found, fetch it from a clerks repository? One might be tempted to write something like:

User user = managers.Get(”Ahmed”);
if (user != null)
{
     // Ahmed is a manager.
     Display(user);
}
else
{
     // Ahmed must be a clerk.
     user = clerks.Get(”Ahmed”);
     Display(user);
}

In the previous examples, we avoided the conditional (null check) by using Special Case. If you look at the requirement for this example, you’ll see that the conditional is built into it, and there is no way to get around it.

But if we use the same technique we used in the second example, we could create an instance of User, that has a boolean property called Exists, which will be populated according to the result. This way, we could express our condition much better:

User user = managers.Get(”Ahmed”);
if (user.Exists)
{
     // Ahmed is a manager.
     Display(user);
}
else
{
     // Ahmed must be a clerk.
     user = clerks.Get(”Ahmed”);
     Display(user);
}

No code saved here, but our intention is much clearer this way.

What the hell is a “if (user != null)”? English, people.

Guys, will you knock it off with returning nulls from methods? You should return Special Cases, not nulls! nulls tend to bypass any polymorphic structure, and cause code to be cluttered with null checks. For example:

public IEnumerable<Picture> GetAllPictures()
{
  if ( .. there are pictures .. )
  {
    return pictures;
  }
  else
  {
    return null;
  }
}

Oh boy, users of this method would have to check for nulls every time before they operate on it: (if they don’t they might get a NullReferenceException, which s-uhhh-cks)

var pictures = GetAllPictures();
if (pictures != null)
{
  foreach (var picture in pictures)
  {
    …
  }
}

Isn’t that null check a big distraction from the actual logic? If you use a Special Case for that enumerable and return Enumerable<Picture>.Empty(), the calling code could be reduced to:

var pictures = GetAllPictures();
foreach (var picture in pictures)
{
  …
}

Much better, no?

A hallway talk at the Alt.NET Israel Unconference got me thinking about coding standards in general, and naming conventions in particular.

I’ve seen dozens of holy wars regarding the subject of naming conventions - when a project starts, when a new team member comes along, when the team leader is replaced etc.

I used to think that a project should have a single naming convention, and everyone should follow it. Now, I’m not so sure any more. I mean, what is really so important about naming conventions? What makes a project with a unified naming convention better than a project without one?

Unity

The first argument for naming conventions is always unity. You want all your data members to look the same.

But, think of it, what is really that important about unity? What business value do you get from it? Does it cut down development time? Does it improve performance?

IMO, if one developer wants his field to be called “_identifier”, another wants “m_identifier” and the other wants “nIdentifier”, just let them! No one ever died from Hungarian notation or a “m_” prefix, I believe.

Readability

For those who still believe in Hungarian notation (or any of its siblings), readability seems to be a great argument for naming conventions.

However, Hungarian notation might have been a good argument a decade ago. Today, all IDE’s provide great intellisense, and one could determine the type of a member in a second by hovering on it.

Scope

Determining the scope of a variable (method or class) is important, but can also be easily discovered by intellisense.

Focus on What’s Important

I’m not trying to say you shouldn’t have a naming convention in your project. I’m just trying to say, don’t let it bother you so much.

Set up a naming convention at the beginning of the project, have your team members agree on it, but don’t hunt down any exception and have it fixed.

Write a unit test or get a cup of coffee instead.

Do you think naming conventions are important? Where would you draw the line?

Krzysztof Cwalina, author of the book Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries has released a second revision of the Framework Design Guidelines Digest.

I’ve read Framework Design Guidelines a couple of years back and learned a whole lot from it. It definitely makes it to my top 5.

However, I’ve had problems convincing my staff members to read it, as it contains~400 pages of design tips, which are quite hard to read in succession.

The Framework Design Guidelines Digest narrows the basics down to 9 pages. I recommend everyone to download and read it every once in a while.

Quoting Krzysztof:

This document is a distillation and a simplification of the most basic guidelines described in detail in a book titled Framework Design Guidelines by Krzysztof Cwalina and Brad Abrams. Framework Design Guidelines were created in the early days of .NET Framework development. They started as a small set of naming and design conventions but have been enhanced, scrutinized, and refined to a point where they are generally considered the canonical way to design frameworks at Microsoft. They carry the experience and cumulative wisdom of thousands of developer hours over several versions of the .NET Framework.

Get it here.