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

Handling Recursion

Handling Recursion

Recursion is a wonderfully geeky word that comes from the Latin word recursio, meaning "to run back."

A recursive procedure (or function, or subroutine) is a procedure that calls itself to do part of the work. The ancients showed the concept of recursion as a snake eating itself.

For a more modern consideration, here's what the dictionary says:

recursion (ri-'ker-zhen) : see recursion

[insert groan here] Recursion in ColdFusion is often done by means of a custom tag. The technique itself is very helpful and can provide functionality that would be difficult to achieve if we didn't have it.

A Case for Recursion
I want to take a look at this technique this month, since it's a topic that often frustrates, even frightens, developers. Let's examine an application written for the megacorporation FuseboxersRus. They've decided to create a human resources application to help the many Fuseboxers that work for the company. They want sections related to employee benefits, company information, internal job openings, and training opportunities.

After discussions and prototyping, we determine that the application will have a simple two-tier architecture. The home circuit will be HumanResources. Underneath it will be circuits for Benefits, Fuse-boxersRus, Openings, and Training (see Figure 1).

Further, while each section should have its own home page, the HR department wants an application home page to look like Figure 2. This single home page, generated by the fuseaction HumanResources.main, actually needs information from each circuit. The stock quote will come from the FuseboxersRus circuit, the job openings from Openings, the training opportunities from Training, and the benefits from Benefits.

Using Recursion to Eliminate Duplicate Code
Duplicating code in both home and individual circuits is bad technique. Instead, let's have each circuit respond to fuseactions specifically designed to return information to the home circuit. For the stock quote the Company circuit responds to the fuseaction request, Company.stock-Quote. The job openings will be handled by Jobs.random3. The fuseaction, Training.upcoming, will provide the information on training opportunities, and we'll get a list of random benefits by executing the fuseaction Benefits.random5 (see Figure 3).

With cases like this - and there are many such cases in creating real-world applications - the best method is to call the application recursively. In effect, we want to suspend processing of the current fuseaction for a moment while we ask the application to return the information we need to complete the waiting fuseaction.

We can do just that with Fusebox 3. Listing 1 is a snippet from the FBX_ Switch.cfm file in the home circuit.

Each <cfmodule> call spawns a separate process, giving us the effect of suspending the original fuseaction while we go out and get the needed information.

The code for the fuseaction is straightforward. The only thing different about it is that it returns information in the caller scope, which is needed so that custom tags can communicate with the pages that called them. If we have code that will be invoked both through a custom tag and normally, this code snippet (placed in the home circuit's FBX_Settings.cfm file) will automatically adjust the scope of the code:

<cfif Fusebox.isCustomTag>
<cfset Scope = "Caller">
<cfset Scope = "Variables">
The variable Fusebox.isCustomTag is part of the application programming interface provided by Fusebox 3. Using this technique you can create applications that are more powerful, tidier, and require less code.

[This article is excerpted from the book Discovering Fusebox, by Hal Helms and John Quarto-vonTivadar.]

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
René Bostic is the Technical VP of the IBM Cloud Unit in North America. Enjoying her career with IBM during the modern millennial technological era, she is an expert in cloud computing, DevOps and emerging cloud technologies such as Blockchain. Her strengths and core competencies include a proven record of accomplishments in consensus building at all levels to assess, plan, and implement enterprise and cloud computing solutions. René is a member of the Society of Women Engineers (SWE) and a m...
Early Bird Registration Discount Expires on August 31, 2018 Conference Registration Link ▸ HERE. Pick from all 200 sessions in all 10 tracks, plus 22 Keynotes & General Sessions! Lunch is served two days. EXPIRES AUGUST 31, 2018. Ticket prices: ($1,295-Aug 31) ($1,495-Oct 31) ($1,995-Nov 12) ($2,500-Walk-in)
Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settlement products to hedge funds and investment banks. After, he co-founded a revenue cycle management company where he learned about Bitcoin and eventually Ethereal. Andrew's role at ConsenSys Enterprise is a mul...
Nicolas Fierro is CEO of MIMIR Blockchain Solutions. He is a programmer, technologist, and operations dev who has worked with Ethereum and blockchain since 2014. His knowledge in blockchain dates to when he performed dev ops services to the Ethereum Foundation as one the privileged few developers to work with the original core team in Switzerland.
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 ...
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.
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 ...
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...