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

All About Arrays: Part 2

All About Arrays: Part 2

In the last issue of CFDJ (December 2002), we looked at arrays, those enormously useful creatures that are underused by some developers. We confined ourselves to one-dimensional arrays - those arrays that look like a single row from a spreadsheet.

When Data Won't Fit into a One-Dimensional Array
But, of course, all data doesn't fit neatly into a single row. Consider, for instance, the case in which we want to keep track of five students who have each taken four tests. We might create a spreadsheet like this to keep track of their test scores:

How, though, do we get that into an array? We can fit those scores into an array only if we can expand our definition of array to mean something more than a single row of values. Luckily we can. We have just such a definition when we explore multidimensional arrays in ColdFusion.

Arrays of Arrays
You can best think of a multidimensional array as an "array of arrays." In the test scores example above, changing the image a bit can be helpful in understanding this concept. For the sake of clarity, I omit the descriptive information that isn't part of the array itself:

Now we have a series of one-dimensional arrays stacked on top of one another. That idea, as we'll see, is key to understanding how to use ColdFusion array functions with multidimensional arrays. But first, let's create this array.

Creating a Two-Dimensional Array
If we only had the first "row" to deal with (the test scores for the first test), creating the array would be easy:

onedee = ArrayNew(1);
onedee[1] = 93;
onedee[2] = 82;
onedee[3] = 99;
onedee[4] = 100;
onedee[5] = 74;

Each number in square brackets (the index) is the number of an associated column. To work with arrays in two dimensions (width and height), we need to use two indices to point at a specific array element. The first index will indicate the row number and the second will indicate its column number. The code for writing the "array of arrays" to keep track of all test scores is just a matter of keeping the row and column numbers straight.

twodee = ArrayNew(2);

twodee[1][1] = 93;
twodee[1][2] = 87;
twodee[1][3] = 99;
twodee[1][4] = 100;
twodee[1][5] = 74;

twodee[2][1] = 89;
twodee[2][2] = 78;
twodee[2][3] = 100;
twodee[2][4] = 82;
twodee[2][5] = 82;

twodee[3][1] = 94;
twodee[3][2] = 84;
twodee[3][3] = 92;
twodee[3][4] = 96;
twodee[3][5] = 84;

twodee[4][1] = 88;
twodee[4][2] = 81;
twodee[4][3] = 100;
twodee[4][4] = 94;
twodee[4][5] = 83;

Accessing Two-Dimensional Array Elements
How did Carla (who's represented by the third column) do on her second test (represented by the second row)? Let's find out:

Carla got a #twodee[2][3]# on her second test.

...and that snippet produces this:
Carla got a 100 on her second test.
How did Ellen do on her first test?

Ellen got a #twodee[1][5]# on her first test.

...which produces: Ellen got a 74 on her first test. Whoops, I guess we shouldn't have asked.

Looping over Two-Dimensional Arrays
Looping over one of these "stacked-up" arrays requires us to use two loops, one nested within the other. Start by looping over the rows and then within this loop, loop over the columns for each row. Here's the code:


That code will produce this screen (see Figure 4):

If you'd like it to look a bit more like a spreadsheet, you can adapt the code so that it places the information in a table:

<table border="thin" bordercolor="silver">

That code produces this screen (see Figure 5):

Working with ColdFusion Array Functions
How do ColdFusion's built-in array functions work on multidimensional arrays? Unfortunately, the ColdFusion documentation does not offer us much guidance on this, so we'll have to put on our lab coats and become scientists. Our first observation should be of the code above that loops over the twodee array. There, we make use of the ArrayLen() function.

The first time we use ArrayLen() is in the outer loop:

<cfloop from="1" to="#ArrayLen(twodee)#" index="rowNumber">

When we use the formulation ArrayLen(array_name), where array_name is a multidimensional array, ColdFusion returns the number of rows in the array, so ArrayLen(twodee) returns "4". But if array_name represents a one-dimensional array, ColdFusion returns the number of columns.

We need to get both rows and columns. Rows, we see, is quite simple - just provide a two-dimensional array to the ArrayLen() function. But to get columns, we must pass ArrayLen() a one-dimensional array - something we don't have. Or do we? Look again at Figure 3. I said that a multidimensional array can be thought of as a series of one-dimensional arrays and one-dimensional arrays are just what we need.

Looked at this way, twodee is a set of four stacked, one-dimensional arrays. We tell ColdFusion that we want to access one of these by providing the array name and an index representing the row number, like this: twodee[1]. That particular formulation represents the first row in our multidimensional array. What number will ArrayLen(twodee[1]) display?

If you said, "five", give yourself full marks. If you said, "four", you might not have seen that, by providing the index along with the array name, we are pointing at the first row, which is a one-dimensional array.

Most of the ColdFusion array functions are designed for one-dimensional arrays and can therefore be used by pointing to a one-dimensional array within a multidimensional array. I've taken the following material from the "ColdFusion Foundations" class I teach, as it illustrates the differences in operation of an array function depending on the type of array. Each of the illustrations assumes the existence of A, a one-dimensional array, and B, a two-dimensional array.

ArrayAppend(A, 'x')
ArrayAppend(B, 'x') Error

ArrayAppend(B[2], 'x')

ArrayAvg(A) 2.5
ArrayAvg(B) Error
ArrayAvg(B[2]) 5

ArrayClear(A) Yes
ArrayClear(B) Yes
ArrayClear(B[2]) Yes

ArrayDeleteAt(A, 2)

ArrayDeleteAt(B, 2)

ArrayDeleteAt(B[2], 2)

ArrayInsertAt(A, 3, 'x')
ArrayInsertAt(B, 2, 'x') Error

ArrayInsertAt(B[2], 2, 'x')

ArrayMax(A) 4
ArrayMax(B) Error
ArrayMax(B[2]) 8

ArrayMin(A) 1
ArrayMin(B) Error
ArrayMin(B[2]) 2

ArrayPrepend(A, 'x')
ArrayPrepend(B, 'x') Error

ArrayPrepend(B[2], 'x')

ArraySet(A, 1, 4, 2)
ArraySet(B, 1, 4, 2) Error

ArraySet(B[2], 1, 4, 2)

ArraySort (B, 'numeric', 'desc') Error

(B[2], 'numeric', 'desc')

ArraySum(A) 10
ArraySum(B) Error
ArraySum(B[2]) 20

ArraySwap(A, 3, 2)

ArraySwap(B, 3, 2)

ArraySwap(B[2], 3, 2)

ArrayToList(A) 1,2,3,4
ArrayToList(B) Error
ArrayToList(B[2], '|') 2|4|6|8

Once arrays are explained, their mystery vanishes and they become just what they were invented to be - extraordinarily helpful constructs that can actually make our code simpler. For more on arrays - including arrays of more than two dimensions - and for some exercises in arrays, go to halhelms.com and test your knowledge of arrays with this month's test/exercise.

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 (3) 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
TenTonJim 02/09/07 05:06:15 PM EST

Great tutorial on the arrays - I am still having trouble though. Say in your example... How would you display a name of the test across the top and the student names down the left column? I have been struggling with this one. Thanks!

Jim S.
Jacksonville, FL USA

Hal Helms 02/13/03 12:03:00 AM EST

Glad to hear that, Mike. They really are very simple if you get started with them in the right way.

Mike Elgers 01/15/03 10:15:00 PM EST

I've never quite understood arrays before and stayed away from them. After reading Hal's article, I think they sound really useful. Well written; I learned a lot.

@ThingsExpo Stories
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend 21st Cloud Expo October 31 - November 2, 2017, at the Santa Clara Convention Center, CA, and June 12-14, 2018, at the Javits Center in New York City, NY, and learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
The current age of digital transformation means that IT organizations must adapt their toolset to cover all digital experiences, beyond just the end users’. Today’s businesses can no longer focus solely on the digital interactions they manage with employees or customers; they must now contend with non-traditional factors. Whether it's the power of brand to make or break a company, the need to monitor across all locations 24/7, or the ability to proactively resolve issues, companies must adapt to...
Artificial intelligence, machine learning, neural networks. We’re in the midst of a wave of excitement around AI such as hasn’t been seen for a few decades. But those previous periods of inflated expectations led to troughs of disappointment. Will this time be different? Most likely. Applications of AI such as predictive analytics are already decreasing costs and improving reliability of industrial machinery. Furthermore, the funding and research going into AI now comes from a wide range of com...
"When we talk about cloud without compromise what we're talking about is that when people think about 'I need the flexibility of the cloud' - it's the ability to create applications and run them in a cloud environment that's far more flexible,” explained Matthew Finnie, CTO of Interoute, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...
SYS-CON Events announced today that MobiDev, a client-oriented software development company, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business...
SYS-CON Events announced today that GrapeUp, the leading provider of rapid product development at the speed of business, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Grape Up is a software company, specialized in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market acr...
SYS-CON Events announced today that Ayehu will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara California. Ayehu provides IT Process Automation & Orchestration solutions for IT and Security professionals to identify and resolve critical incidents and enable rapid containment, eradication, and recovery from cyber security breaches. Ayehu provides customers greater control over IT infras...
In this presentation, Striim CTO and founder Steve Wilkes will discuss practical strategies for counteracting fraud and cyberattacks by leveraging real-time streaming analytics. In his session at @ThingsExpo, Steve Wilkes, Founder and Chief Technology Officer at Striim, will provide a detailed look into leveraging streaming data management to correlate events in real time, and identify potential breaches across IoT and non-IoT systems throughout the enterprise. Strategies for processing massive ...
SYS-CON Events announced today that Cloud Academy named "Bronze Sponsor" of 21st International Cloud Expo which will take place October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara, CA. Cloud Academy is the industry’s most innovative, vendor-neutral cloud technology training platform. Cloud Academy provides continuous learning solutions for individuals and enterprise teams for Amazon Web Services, Microsoft Azure, Google Cloud Platform, and the most popular cloud com...
In his session at Cloud Expo, Alan Winters, an entertainment executive/TV producer turned serial entrepreneur, presented a success story of an entrepreneur who has both suffered through and benefited from offshore development across multiple businesses: The smart choice, or how to select the right offshore development partner Warning signs, or how to minimize chances of making the wrong choice Collaboration, or how to establish the most effective work processes Budget control, or how to ma...
SYS-CON Events announced today that Enzu will exhibit at SYS-CON's 21st Int\ernational Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their ...
We build IoT infrastructure products - when you have to integrate different devices, different systems and cloud you have to build an application to do that but we eliminate the need to build an application. Our products can integrate any device, any system, any cloud regardless of protocol," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA
SYS-CON Events announced today that IBM has been named “Diamond Sponsor” of SYS-CON's 21st Cloud Expo, which will take place on October 31 through November 2nd 2017 at the Santa Clara Convention Center in Santa Clara, California.
SYS-CON Events announced today that CA Technologies has been named "Platinum Sponsor" of SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business - from apparel to energy - is being rewritten by software. From planning to development to management to security, CA creates software that fuels transformation for companies in the applic...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assista...
Multiple data types are pouring into IoT deployments. Data is coming in small packages as well as enormous files and data streams of many sizes. Widespread use of mobile devices adds to the total. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists looked at the tools and environments that are being put to use in IoT deployments, as well as the team skills a modern enterprise IT shop needs to keep things running, get a handle on all this data, and deliver...
In his session at @ThingsExpo, Eric Lachapelle, CEO of the Professional Evaluation and Certification Board (PECB), provided an overview of various initiatives to certify the security of connected devices and future trends in ensuring public trust of IoT. Eric Lachapelle is the Chief Executive Officer of the Professional Evaluation and Certification Board (PECB), an international certification body. His role is to help companies and individuals to achieve professional, accredited and worldwide re...
With the introduction of IoT and Smart Living in every aspect of our lives, one question has become relevant: What are the security implications? To answer this, first we have to look and explore the security models of the technologies that IoT is founded upon. In his session at @ThingsExpo, Nevi Kaja, a Research Engineer at Ford Motor Company, discussed some of the security challenges of the IoT infrastructure and related how these aspects impact Smart Living. The material was delivered interac...
IoT solutions exploit operational data generated by Internet-connected smart “things” for the purpose of gaining operational insight and producing “better outcomes” (for example, create new business models, eliminate unscheduled maintenance, etc.). The explosive proliferation of IoT solutions will result in an exponential growth in the volume of IoT data, precipitating significant Information Governance issues: who owns the IoT data, what are the rights/duties of IoT solutions adopters towards t...