|By Ray Camden||
|August 23, 2002 12:00 AM EDT||
Because ColdFusion components are such a new feature, developers may not yet have a good idea of what constitutes best practices.
This article attempts to rectify that situation by enumerating a set of guidelines that should be used when designing and working with CFCs, one of the most interesting new features of ColdFusion MX. Bear in mind that because they're so new, even experienced developers are debating what makes sense as a "best practice." These types of articles are always a matter of contention. I encourage you to contact me or discuss the article on any of the public lists, such as this magazine's CFDJ-List. The best way we as developers can improve our own code is by discussing our methods with others. With that in mind, let's begin...
Normally a CFC is composed of a large set of methods. Let's discuss a few things to remember when building methods.
By default, all CFC methods have an access="public" setting. A method can have four different types of access. Public means that the method can be called from the local server or from instances of the CFC. The other settings are private, package, and remote. Private methods can be called only from other methods in the CFC itself. Package methods are those that can be called from other CFCs in the same package. Remote, the most open setting, can be called from any source, including remote servers and Flash files.
It's important that you remember the default setting of "public." While it's not as open as "remote," it may not be what you intend when designing your CFC. A simple way to handle this is to set all methods in the CFC to "private." This means your methods will be as secure as possible. "Open" up your methods only on a case by case basis. If you want to be truly anal (and when it comes to security, you can't be too anal), follow this practice even when you're "really, really" sure the method will be used publicly. Wait until you actually code the CFM that will call the CFC's method. At that point you can change the method being called.
The CFFUNCTION tag takes multiple attributes, many of which are optional. It's best to explicitly set most, or all, of them. At its basic level, CFFUNCTION needs a "name" attribute. However, each of the following attributes should be passed:
Let's take a look at a method with the barest essentials set:
<cffunction name="cartTotal">Now compare this to a method with most of the optional attributes set. It's much clearer what the method is doing and how it will return information.
... method code ...
<cffunction name="cartTotal"" output="false" access="private"
hint="This method calculates the total
price of all the items in the shopping cart.
It simply loops over the cart and multiplies
item price by quantity.">
We can also apply this same principle to the CFARGUMENT tag. CFARGUMENT, like CFFUNCTION, requires only the "name" attribute. However, you can - and should - pass the following optional arguments:
Once again, let's take a look at a method that doesn't use these optional attributes:
<cffunction name="cartTotal">Now consider the version in Listing 1. As you can see, the second version of the method is much clearer about what exactly it does.
... method code ...
Output vs Return
When calling a method on a CFC, you can display the output in multiple ways. The method itself can CFOUTPUT data or it can return the data to the caller. You should never CFOUTPUT. Instead, data should be returned by using the CFRETURN tag. There are a number of reasons for this. If you ever encounter a case where you don't want the result of the method displayed immediately (maybe you want to store the result in a database), you'll have to reengineer your method and any calls to it (unless you use CFSAVECONTENT to suppress the output).
Another reason not to use CF OUTPUT is because of a bug with persistent components. If you store an instance of a component in a persistent scope (like the Session scope), and if you call a method that outputs instead of returns data, you'll only be able to call it once. Any subsequent call will not display the output.
The most important reason not to output directly from the CFC is Flash. Any data that isn't returned from the method will not be usable from Flash applications that use your CFC. By using CFRETURN, you guarantee that it will work with both your CFML files and your Flash files.
Use the Var Scope
If you've read anything about user-defined functions, you've probably seen mention of the "Var" scope. This is a scope created specifically for the lifetime of the function. By creating data in this scope, you help ensure that a UDF doesn't accidentally overwrite variables in the template. The Var scope is just as important when working with CFC methods. Consider the following CFC method:
<cffunction name="returnFoo" output="false"This function simply sets x to 1 and y to the value of another method in the CFC, and then returns the value of x. You'd expect this method to return 1. However, guess what happens if returnGoo looks like the following:
hint="Returns the value of Foo">
<cfset x = 1>
<cfset y = returnGoo(x)>
<cffunction name="returnGoo" output="false"You might expect this to have no impact on our original function, returnFoo, but because the x value was never Var scoped, instead of getting 1 back, we get 100. To correct this we can simply add the Var qualifier to the sets in each method:
hint="Returns the value of Goo">
<cfset x = 100>
<cffunction name="returnFoo" output="false"Once this is done, calling return-Foo returns the value we expect, 1.
hint="Returns the value of Foo">
<cfset var x = 1>
<cfset var y = returnGoo(x)>
<cffunction name="returnGoo" output="false"
hint="Returns the value of Goo">
<cfset var x = 100>
Don't forget that any and all Var statements must be made before any real code. They should be placed immediately after any CFARGUMENT tag.
Another aspect of CFCs is the use of component data. This is data that persists for the lifetime of the CFC and is accessible to both the methods of the CFC and, potentially, the template using the CFC.
The This Scope
Two scopes can be used with CFCs. The first one, which will be used most of the time, is the This scope. Values can be defined in this scope just as in any other:
<cfset this.name = "Raymond">
Any variable defined in this scope is available to the calling template. For example:
<cfset theOb = createObject("component","test")>Conversely, if you pass a value to a CFC, it will automatically be placed in the This scope. Consider:
<cfset theOb = createObject("component","test")>Once the CFSET command is run, any method will have access to foo in the This scope.
<cfset theOb.foo = 1>
What are some things to consider when storing information in a CFC? Any information placed in the This scope is public. It can be read by the calling template and even changed. This is fine if you don't mind the information being manipulated. However, you may not always want that. If you have information that you want to persist in the CFC without possibly exposing it, simply leave off the This scope. Imagine the following code in a CFC:
<cfset this.name = "Raymond">This code creates two variables in the CFC. The first is a public variable called name. The second variable, id, is not public. There isn't a real name for this scope. I refer to it as a private scope. It's not the same as the Variables scope and you can't CFDUMP it, but it's a useful way to store data and keep it separate from the public variables.
<cfset id = createUUID()>
The CFPROPERTY tag, technically, serves little purpose for CFCs. Its main use is to help define return values for Web services. However, it can serve a useful purpose for CFCs as well. The first thing to remember is that the CFPROPERTY tag will not actually do anything at runtime. Consider the following line of code:
<cfproperty name="numberOfLegs" type="numeric" required="true">
While it looks like it may add a level of validation to the tag, it really just defines metadata for the CFC. In other words, it helps describe it. The only required attribute is name. Everything else simply helps describe the property. This can be useful in multiple ways. First of all, it shows up in the descriptor. Second, every attribute passed in is available via the getMetaData function. This means you could write your own validation routines. Consider the following CFPROPERTY tag:
<cfproperty name="numberOfLegs" type="numeric" required="true" range="1,8">
The range attribute isn't a real attribute, but it will show up in the metadata. It would be trivial then to write a method that validates the value for this.numberOfLegs to ensure that it falls between 1 and 8. As you can imagine, this is pretty open ended. Any attribute to CFPROPERTY can be passed and used. How it's implemented is completely up to the developer.
That's Not All, Folks...
As I said at the beginning, CFCs are a new feature. What makes sense to me, and others, at this point will seem a bit silly next year (or even a few months from now). If you have any ideas you'd like to add, or perhaps you see something you disagree with, please e-mail me. You should also visit www.CFCZone.org. This is a site run by Rob Brooks-Bilson. (It's in the same vein as www.CFLib.org.) The site will soon host free, and open source, CFCs that you can use in your own projects.
The BPM world is going through some evolution or changes where traditional business process management solutions really have nowhere to go in terms of development of the road map. In this demo at 15th Cloud Expo, Kyle Hansen, Director of Professional Services at AgilePoint, shows AgilePoint’s unique approach to dealing with this market circumstance by developing a rapid application composition or development framework.
Dec. 20, 2014 07:00 PM EST Reads: 1,184
ARMONK, N.Y., Nov. 20, 2014 /PRNewswire/ -- IBM (NYSE: IBM) today announced that it is bringing a greater level of control, security and flexibility to cloud-based application development and delivery with a single-tenant version of Bluemix, IBM's platform-as-a-service. The new platform enables developers to build ap...
Dec. 20, 2014 12:30 PM EST Reads: 2,069
"BSQUARE is in the business of selling software solutions for smart connected devices. It's obvious that IoT has moved from being a technology to being a fundamental part of business, and in the last 18 months people have said let's figure out how to do it and let's put some focus on it, " explained Dave Wagstaff, VP & Chief Architect, at BSQUARE Corporation, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 20, 2014 12:00 PM EST Reads: 1,933
The major cloud platforms defy a simple, side-by-side analysis. Each of the major IaaS public-cloud platforms offers their own unique strengths and functionality. Options for on-site private cloud are diverse as well, and must be designed and deployed while taking existing legacy architecture and infrastructure into account. Then the reality is that most enterprises are embarking on a hybrid cloud strategy and programs. In this Power Panel at 15th Cloud Expo (http://www.CloudComputingExpo.com), moderated by Ashar Baig, Research Director, Cloud, at Gigaom Research, Nate Gordon, Director of T...
Dec. 20, 2014 11:30 AM EST Reads: 2,372
The Internet of Things is not new. Historically, smart businesses have used its basic concept of leveraging data to drive better decision making and have capitalized on those insights to realize additional revenue opportunities. So, what has changed to make the Internet of Things one of the hottest topics in tech? In his session at @ThingsExpo, Chris Gray, Director, Embedded and Internet of Things, discussed the underlying factors that are driving the economics of intelligent systems. Discover how hardware commoditization, the ubiquitous nature of connectivity, and the emergence of Big Data a...
Dec. 20, 2014 11:00 AM EST Reads: 2,257
SYS-CON Events announced today that Windstream, a leading provider of advanced network and cloud communications, has been named “Silver Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. Windstream (Nasdaq: WIN), a FORTUNE 500 and S&P 500 company, is a leading provider of advanced network communications, including cloud computing and managed services, to businesses nationwide. The company also offers broadband, phone and digital TV services to consumers primarily in rural areas.
Dec. 20, 2014 10:45 AM EST Reads: 2,227
“In the past year we've seen a lot of stabilization of WebRTC. You can now use it in production with a far greater degree of certainty. A lot of the real developments in the past year have been in things like the data channel, which will enable a whole new type of application," explained Peter Dunkley, Technical Director at Acision, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 20, 2014 08:00 AM EST Reads: 1,292
SYS-CON Events announced today that IDenticard will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. IDenticard™ is the security division of Brady Corp (NYSE: BRC), a $1.5 billion manufacturer of identification products. We have small-company values with the strength and stability of a major corporation. IDenticard offers local sales, support and service to our customers across the United States and Canada. Our partner network encompasses some 300 of the world's leading systems integrators and security s...
Dec. 20, 2014 07:00 AM EST Reads: 2,094
DevOps Summit 2015 New York, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that it is now accepting Keynote Proposals. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long development cycles that produce software that is obsolete at launch. DevOps may be disruptive, but it is essential.
Dec. 18, 2014 09:45 PM EST Reads: 1,119
"People are a lot more knowledgeable about APIs now. There are two types of people who work with APIs - IT people who want to use APIs for something internal and the product managers who want to do something outside APIs for people to connect to them," explained Roberto Medrano, Executive Vice President at SOA Software, in this SYS-CON.tv interview at Cloud Expo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 18, 2014 09:00 AM EST Reads: 1,345
Nigeria has the largest economy in Africa, at more than US$500 billion, and ranks 23rd in the world. A recent re-evaluation of Nigeria's true economic size doubled the previous estimate, and brought it well ahead of South Africa, which is a member (unlike Nigeria) of the G20 club for political as well as economic reasons. Nigeria's economy can be said to be quite diverse from one point of view, but heavily dependent on oil and gas at the same time. Oil and natural gas account for about 15% of Nigera's overall economy, but traditionally represent more than 90% of the country's exports and as...
Dec. 18, 2014 06:00 AM EST Reads: 886
The Internet of Things is a misnomer. That implies that everything is on the Internet, and that simply should not be - especially for things that are blurring the line between medical devices that stimulate like a pacemaker and quantified self-sensors like a pedometer or pulse tracker. The mesh of things that we manage must be segmented into zones of trust for sensing data, transmitting data, receiving command and control administrative changes, and peer-to-peer mesh messaging. In his session at @ThingsExpo, Ryan Bagnulo, Solution Architect / Software Engineer at SOA Software, focused on desi...
Dec. 17, 2014 11:15 PM EST Reads: 1,375
"At our booth we are showing how to provide trust in the Internet of Things. Trust is where everything starts to become secure and trustworthy. Now with the scaling of the Internet of Things it becomes an interesting question – I've heard numbers from 200 billion devices next year up to a trillion in the next 10 to 15 years," explained Johannes Lintzen, Vice President of Sales at Utimaco, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 17, 2014 11:00 PM EST Reads: 1,434
"For over 25 years we have been working with a lot of enterprise customers and we have seen how companies create applications. And now that we have moved to cloud computing, mobile, social and the Internet of Things, we see that the market needs a new way of creating applications," stated Jesse Shiah, CEO, President and Co-Founder of AgilePoint Inc., in this SYS-CON.tv interview at 15th Cloud Expo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Dec. 17, 2014 08:00 PM EST Reads: 1,420
SYS-CON Events announced today that Gridstore™, the leader in hyper-converged infrastructure purpose-built to optimize Microsoft workloads, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Gridstore™ is the leader in hyper-converged infrastructure purpose-built for Microsoft workloads and designed to accelerate applications in virtualized environments. Gridstore’s hyper-converged infrastructure is the industry’s first all flash version of HyperConverged Appliances that include both compute and storag...
Dec. 17, 2014 06:30 PM EST Reads: 1,331
Today’s enterprise is being driven by disruptive competitive and human capital requirements to provide enterprise application access through not only desktops, but also mobile devices. To retrofit existing programs across all these devices using traditional programming methods is very costly and time consuming – often prohibitively so. In his session at @ThingsExpo, Jesse Shiah, CEO, President, and Co-Founder of AgilePoint Inc., discussed how you can create applications that run on all mobile devices as well as laptops and desktops using a visual drag-and-drop application – and eForms-buildi...
Dec. 17, 2014 11:45 AM EST Reads: 1,542
We certainly live in interesting technological times. And no more interesting than the current competing IoT standards for connectivity. Various standards bodies, approaches, and ecosystems are vying for mindshare and positioning for a competitive edge. It is clear that when the dust settles, we will have new protocols, evolved protocols, that will change the way we interact with devices and infrastructure. We will also have evolved web protocols, like HTTP/2, that will be changing the very core of our infrastructures. At the same time, we have old approaches made new again like micro-services...
Dec. 16, 2014 11:45 PM EST Reads: 1,376
Code Halos - aka "digital fingerprints" - are the key organizing principle to understand a) how dumb things become smart and b) how to monetize this dynamic. In his session at @ThingsExpo, Robert Brown, AVP, Center for the Future of Work at Cognizant Technology Solutions, outlined research, analysis and recommendations from his recently published book on this phenomena on the way leading edge organizations like GE and Disney are unlocking the Internet of Things opportunity and what steps your organization should be taking to position itself for the next platform of digital competition.
Dec. 15, 2014 11:45 PM EST Reads: 1,723
The 3rd International Internet of @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that its Call for Papers is now open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
Dec. 15, 2014 10:30 AM EST Reads: 6,905
As the Internet of Things unfolds, mobile and wearable devices are blurring the line between physical and digital, integrating ever more closely with our interests, our routines, our daily lives. Contextual computing and smart, sensor-equipped spaces bring the potential to walk through a world that recognizes us and responds accordingly. We become continuous transmitters and receivers of data. In his session at @ThingsExpo, Andrew Bolwell, Director of Innovation for HP's Printing and Personal Systems Group, discussed how key attributes of mobile technology – touch input, sensors, social, and ...
Dec. 15, 2014 10:00 AM EST Reads: 1,978