Welcome!

You will be redirected in 30 seconds or close now.

ColdFusion Authors: Yakov Fain, Jeremy Geelan, Maureen O'Gara, Nancy Y. Nee, Tad Anderson

Related Topics: ColdFusion

ColdFusion: Article

Toward a New Orthodoxy – Dynamic Typing

Toward a New Orthodoxy

Last month, we took a long look at strong typing. We saw that while strong typing offers many benefits in a language such as Java, trying to attach strong typing to ColdFusion produces really difficult problems. And last month, due to my "in" connections, we were even able to briefly interview the Java compiler.

Some might have thought that I was arguing the case against strong/static typing, as many developers have recently. They have argued that static typing is an emperor without clothes. Bruce Eckel, of Thinking in Java fame, has called strong typing "a Faustian bargain." Guido van Rossum, creator of Python, has said, "Strong typing catches many bugs, but it also makes you focus too much on getting the types right and not enough on getting the rest of the program right." Developer Ned Batchelder has summed up the case against strong typing: Static typing prevents certain kinds of failures. Unfortunately, it also prevents certain kinds of successes."

My own view of strong/static typing is different: I find it immensely helpful in a language like Java. I think that a good deal of the problems developers have with strong typing in that language would be greatly ameliorated by designing with interfaces. And I appear to be in good company. The "Gang of Four" authors who wrote the seminal work, Design Patterns, offered readers the excellent advice: "Design to interfaces, not to implementations."

Clearly, the issue of strong versus weak / static versus dynamic typing is one on which many smart and experienced developers disagree. In this article, I want to make a case that, whatever your view of strong/static typing is, in regards to ColdFusion, it is a moot point simply because ColdFusion does not support strong typing.

But is this a defect in ColdFusion or merely a difference? Certainly languages such as Smalltalk, Python, and Ruby seem to do fine without strong typing. To that illustrious list, I would add ColdFusion.

In place of the debate over whether strong or weak typing is better, perhaps a better question is this: How can we benefit from the dynamic typing ColdFusion offers? First, I think we would do well to adopt what Dave Thomas (The Pragmatic Programmers) whimsically calls duck typing - as in, "if it walks like a duck and quacks like a duck, it must be a duck!"

With duck typing, the idea of a type becomes more a matter of "Can this object respond to this message?" rather than "Does this object fit into a type hierarchy?". This is particularly important with ColdFusion since the only type hierarchy available is one of inheritance, which commonly causes fragile code.

Let's look at an example of duck typing. Having just returned from teaching two classes in Las Vegas, I'll use an example from the poker craze that has turned ordinarily calm souls into wild men (and women!) pushing their entire stack of chips into the pot while calling "All in!" Let's suppose that we've been asked to come up with a domain model for a Las Vegas poker room.

We might begin with a Player CFC that has the following methods:

  • bet (accepts a numeric value)
  • check
  • fold
  • raise (accepts a numeric value)
We probably also want a Dealer CFC with these methods:
  • dealHoleCards
  • promptPlayer
  • acceptBet (accepts a numeric value)
  • dealFlop
  • dealTurn
  • dealRiver
  • declareWinner
Perhaps, we'll have an Employee class that Dealer inherits. No doubt an Employee will have many methods but the one closest to our hearts is this:
  • acceptPay (accepts a numeric value)
Now, a little known fact is that many Las Vegas poker rooms employ proposition player (or simply props). Prop players are paid by the house to stimulate action, but play with their own money. Since prop players are paid by the house, our Prop class might rightfully extend Employee.

But, let's suppose that we need to model a tournament. Our Tournament CFC could have methods like:

  • register (accepts a Player and a numeric amount)
  • payWinners
We run into a problem here. It may be that in order to fill a tournament, the house asks a prop to enter a tournament. But the Tournament's register method accepts only Player objects. In a strongly typed system, we really want our Prop players to be of both Employee and Player types.

Java solves this problem through interfaces. A class can extend only one superclass, but it can implement as many interfaces as needed. Interfaces define a type and the methods that can be called on that type, but provide no method bodies - that is, no implementations of these methods. Assuming we want Prop to extend Employee (and that ColdFusion had interfaces), we could provide a Player interface that would be functionally similar to this Java version:

public interface Player{
    public void bet(int bet);
    public void check();
    public void fold();
    public void raise(int bet);
}

Interfaces provide type inheritance, but not code inheritance: the implementing class must provide the method bodies for all methods defined in the interfaces it implements. While this does solve the problem of multiple-typing, it does so at a cost. If we need to change the implementation of a Player, it must be done in both the Player class and the Prop class. This violates what is sometimes called the DRY (Don't Repeat Yourself) principle. According to Dave Thomas, "DRY says that every piece of system knowledge should have one authoritative, unambiguous representation." Here, we have (at least) two representations for each Player method.

For the many ColdFusion developers who dutifully provide type properties for their arguments and returntype properties for their methods, this has caused ineluctable problems that have not been resolved. But again, let's ask the question: Is this a defect in ColdFusion or merely a difference?

If we embrace ColdFusion's weak typing, there is no problem. As long as both the Player object and the Prop object can respond to the methods needed to play in the tournament (bet, check, fold, and raise), our code will run without a snag. "But it's not type safe!" the strong type proponent might argue. That's true, but ColdFusion doesn't offer type safety (nor do Smalltalk, Python, or Ruby). We might say that if an object can bet, check, fold, and raise like a Player, then it is a Player - regardless of its class.

Welcome to duck typing. All that is required is that we give up the illusion of type safety (and with it, the returntype and type properties of methods and arguments, respectively). And there are other benefits to duck typing. One informal study found that Java applications compared to the same applications in Smalltalk required between 85-230% more code. That's a lot of finger typing.

Of course, speed doesn't mean much if we are writing fragile code that will be hard to maintain. Since the overwhelming majority of the cost of code over its lifetime is spent on maintenance, anything that compromises the maintainability of code must be highly suspect. And strong typing must be credited with catching many errors that may not be at first apparent, but which will surface over an application's lifetime.

As you might guess, the duck typers have an answer for this: unit testing. Unit testing is a part of a movement/philosophy known as test-driven development. In test-driven development, automated tests are written as part of the software design cycle. Such tests act like "mini clients," exercising the various methods of each class to uncover any bugs.

For such testing to be feasible, it must be automated. Kent Beck and Erich Gamma produced a tool to do just this for Java programmers: JUnit. It has since been implemented in many languages. ColdFusion has two programs that provide automated test unit functionality, CFCUnit (www.cfcUnit.com) and CFUnit (www.cfunit.sourceforge.net). I strongly encourage readers to explore the difference using such tools can have on the quality of your software.

Perhaps you noticed that something was left out of our duck typing solution to the problem of prop players. If both the Prop and the Player classes have to independently implement the various player methods, are we not still in violation of the DRY principle? We are. The solution to this problem comes from applying the notion of mixins to ColdFusion.

Mixins are a technique, first introduced in a Lisp language variant known as Flavors, in which a class defines the attributes of the class, but does not define the methods of the class. Instead, the methods are defined in separate files known as mixins. In our example, both the Prop and the Player class would define their own instance variables, but would include the methods for bet, check, fold, and raise from a separate file - perhaps PlayerMixin.

The good news is that ColdFusion makes the use of mixins very simple and straightforward. Next month, we'll look at code that makes use of mixins and we'll see how mixins can either be applied to an entire class or to individual objects.

More Stories By Hal Helms

Hal Helms is a well-known speaker/writer/strategist on software development issues. He holds training sessions on Java, ColdFusion, and software development processes. He authors a popular monthly newsletter series. For more information, contact him at hal (at) halhelms.com or see his website, www.halhelms.com.

Comments (1) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
Mark Gaulin 01/24/06 09:42:43 AM EST

Strong typing is extremely helpful when doing refactoring. I'm sure that there is lots of weakly-typed code out there that people are just plain afraid to improve (through refactoring) because they can't easily find and adjust existing references to an "interface" (be it a class definition (or cfc), or a function call (or custom tag)).

Refactoring is extremely important to a code base's long-term health and usefulness. Code that just "works", but cannot easily evolve, rots on the vine.

IoT & Smart Cities Stories
The challenges of aggregating data from consumer-oriented devices, such as wearable technologies and smart thermostats, are fairly well-understood. However, there are a new set of challenges for IoT devices that generate megabytes or gigabytes of data per second. Certainly, the infrastructure will have to change, as those volumes of data will likely overwhelm the available bandwidth for aggregating the data into a central repository. Ochandarena discusses a whole new way to think about your next...
CloudEXPO | DevOpsSUMMIT | DXWorldEXPO are the world's most influential, independent events where Cloud Computing was coined and where technology buyers and vendors meet to experience and discuss the big picture of Digital Transformation and all of the strategies, tactics, and tools they need to realize their goals. Sponsors of DXWorldEXPO | CloudEXPO benefit from unmatched branding, profile building and lead generation opportunities.
All in Mobile is a place where we continually maximize their impact by fostering understanding, empathy, insights, creativity and joy. They believe that a truly useful and desirable mobile app doesn't need the brightest idea or the most advanced technology. A great product begins with understanding people. It's easy to think that customers will love your app, but can you justify it? They make sure your final app is something that users truly want and need. The only way to do this is by ...
Digital Transformation and Disruption, Amazon Style - What You Can Learn. Chris Kocher is a co-founder of Grey Heron, a management and strategic marketing consulting firm. He has 25+ years in both strategic and hands-on operating experience helping executives and investors build revenues and shareholder value. He has consulted with over 130 companies on innovating with new business models, product strategies and monetization. Chris has held management positions at HP and Symantec in addition to ...
DXWorldEXPO LLC announced today that Big Data Federation to Exhibit at the 22nd International CloudEXPO, colocated with DevOpsSUMMIT and DXWorldEXPO, November 12-13, 2018 in New York City. Big Data Federation, Inc. develops and applies artificial intelligence to predict financial and economic events that matter. The company uncovers patterns and precise drivers of performance and outcomes with the aid of machine-learning algorithms, big data, and fundamental analysis. Their products are deployed...
Dynatrace is an application performance management software company with products for the information technology departments and digital business owners of medium and large businesses. Building the Future of Monitoring with Artificial Intelligence. Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more busine...
Cell networks have the advantage of long-range communications, reaching an estimated 90% of the world. But cell networks such as 2G, 3G and LTE consume lots of power and were designed for connecting people. They are not optimized for low- or battery-powered devices or for IoT applications with infrequently transmitted data. Cell IoT modules that support narrow-band IoT and 4G cell networks will enable cell connectivity, device management, and app enablement for low-power wide-area network IoT. B...
The hierarchical architecture that distributes "compute" within the network specially at the edge can enable new services by harnessing emerging technologies. But Edge-Compute comes at increased cost that needs to be managed and potentially augmented by creative architecture solutions as there will always a catching-up with the capacity demands. Processing power in smartphones has enhanced YoY and there is increasingly spare compute capacity that can be potentially pooled. Uber has successfully ...
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things'). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing. IoT is not about the devices, its about the data consumed and generated. The devices are tools, mechanisms, conduits. This paper discusses the considerations when dealing with the...