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

Mixins

Writing software that's more flexible and maintainable

In the last two installments of "Foundations," we looked at the issue of static v dynamic typing in ColdFusion and I argued that treating ColdFusion as a statically typed language led to disappointment and defeat. In this issue let's explore some of the possibilities available when we no longer treat ColdFusion as "Java Lite" but accept it on its own terms..

What Are "Mixins"?
In the late 1970s, a Lisp-based language called "Flavors", originating at M.I.T., introduced the idea of adding functionality from one class to another. The term, mixin, was apparently inspired by some of the ice cream parlors around the M.I.T. campus that offered customers the option of mixing such goodies as Oreos and candy bars into their standard ice cream flavors.

I've been working with Ruby lately, which also offers mixins, and I began to wonder if, freed from the constraints of static typing, (1) it might be possible and, (2) we might benefit from implementing mixins in ColdFusion.

After some thinking, talking with colleagues, and experimenting, I came up with two methods of introducing mixins and I've given them the names class-based mixins and object-based mixins. Both are quite useful but work very differently.

Class-Based Mixins
In the November issue of CFDJ, I explained how Java interfaces are used to provide for multiple-type inheritance while avoiding the problems of code conflict that multiple inheritance languages must deal with.

Java interfaces are wonderful - for Java - but they do violate a sound fundamental of creating software, dubbed the DRY (Don't Repeat Yourself) Principle. In an interview, Dave Thomas (of The Pragmatic Programmer fame) had this to say about DRY: "DRY says that every piece of system knowledge should have one authoritative, unambiguous representation."

Java interfaces push the "authoritative, unambiguous representation" of methods down to the implementing classes. There are many situations that arise where multiple implementing classes of a single interface will mean multiple code implementations.

Let me offer some example Java code to illustrate:

public interface Teacher{
     public void giveTest(Test test);
}

Here we have a very simple interface, defining what it means to be a teacher: a teacher is someone who can give a test. What does it mean to give a test? For our purposes, let's say that it entails the following:

  1. Give out Test booklets
  2. Answer any questions about the test
  3. Monitor the students
  4. Monitor the time
  5. Collect the test booklets at the end of the allotted time
Initially I want to have a Teacher class that implements the Teacher interface. It might look something like this:

public class Teacher implements interfaces.Teacher{
    private String name = null;

    public Teacher(String name){
      setName(name);
    }

    public void giveTest(Test test){
      giveOutTestBooklets(test);
      monitorStudents();
      monitorTime(test);
      collectTestBooklets();
    }
    // giveOutTestBooklets, monitor Students, monitorTime,
    // and collectTestBooklets methods below...
}

Now, I'll implement the Teacher interface in another class - say, StudentTeacher:

public class StudentTeacher extends Student implements Teacher{

    public StudentTeacher(){
      // default constructor
    }

    public void giveTest(Test test){
      giveOutTestBooklets(test);
      monitorStudents();
      monitorTime(test);
      collectTestBooklets();
    }
    // giveOutTestBooklets, monitor Students, monitorTime,
    // and collectTestBooklets methods below...
}

That doesn't look like one representation to me: we have a lot of duplicated code. Fortunately, class-based mixins can help us. Let's tackle the same problem but with ColdFusion with class-based mixins.

Our first step is to create a single representation of a teacher. We'll save this as a ColdFusion template (not a CFC) called Teacher:

<cfset variables.instance.name = null />

<cffunction name="init" access="public" output="false">
     <cfargument name="name" required="true" />
     <cfset set('name', arguments.name) />
     <cfreturn this />
</cffunction>

<cffunction name="giveTest" access="public" output="false">
     <cfargument name="test" required="true" />
     <cfset giveOutTestBooklets(arguments.test) />
     <cfset monitorStudents() />
     <cfset monitorTime(arguments.test) />
     <cfset collectTestBooklets() />
</cffunction>

<!--- other methods below... --->

This is the code we're going to mix into classes. Our first class is Teacher.cfc:

<cfcomponent displayname="Teacher" extends="BaseComponent">
    <cfinclude template="Teacher.cfm" />

    <cffunction name="init" access="public" output="false">
      <cfargument name="test" required="true" />
      <cfset set('test', arguments.test) />
      <cfreturn this />
    </cffunction>
</cfcomponent>

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 (0)

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.


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...
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...
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 ...
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.
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 ...
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...