|By Steve Parks||
|November 19, 2002 12:00 AM EST||
In computer terms, objects are abstracts of real-world entities that are all around us in everyday life. Examples of such objects could be people, organizations, cars, animals, or even less tangible entities such as math or time.
Of these examples, only the first four can be considered collections. One or more persons is a collection of people; one or more organizations is a collection of organizations, and so on. However, math is not a collection of math and time is not a collection of time. They are just simple objects with methods and properties. Simply defined, a collection is a set of related objects.
Collections come with many advantages. First, they are objects, so any and all advantages of objects, such as encapsulation and reusability, are inherent to the collection. Second, you can access a group of objects easily by looping through the collection and executing the same code against each object in the collection. Finally, you can simplify a lot of the external data manipulation by using collections. For instance, instead of returning a query containing users (which might change in six months) you could use a Users collection. The User object that is stored in the Users collection would encapsulate all the code that goes into retrieving the user data. That way, when the database changes, you can change your User object while your collection and the code accessing the collection remain the same.
What Makes a Collection?
There are three hard and fast rules that an object (or in ColdFusion, a component) has to adhere to in order to be a collection:
1. Every object in the collection can be accessed individually. Each object in the collection is unique in instance, if not data. If there are five objects in the collection, you should be able to call properties and methods from each object.
2. Every object in the collection is the same type of object and has the same properties and methods. This means that you wouldn't have a collection called People with two types of objects: People and Computers. You would, in fact, have two collections, the People collection and the Computers collection.
3. A collection usually has at least four methods: Add, Remove, Count, and Item.
Most collections can be completely accessed through the use of just four methods:
Creating the Collection Files
In order to create a collection we need to create two files, both of which are CFCs. The first CFC we'll create will be named ActiveUsers.cfc; the second will be named ActiveUser.cfc. The ActiveUser.cfc file will be the actual object that is contained in our collection. The collection filename is usually the plural term for the name of our object, hence, ActiveUser object and ActiveUsers collection. The ActiveUser.cfc file is shown in Listing 1.
The ActiveUsers collection will have four methods: Add(strFirstName, strLastName), Remove(index), Item(index), and Count(). Our ActiveUser object will contain five methods: GetName(), SetName(strFirstName, strLastName), SetLoginTime(), GetLoginTime(), and GetMinutesActive().
Our ActiveUsers collection will be used to display only users who are currently active on our Web site, similar to a "who's on" interface. Anytime you access a variable in a shared scope, such as the Application scope, you should lock it using CFLOCK.
The first step is to set up a data structure to store our data in the ActiveUsers collection. We need only one private (or member) variable called arItems, which is an array. You can add that code just inside of your CFCOMPONENT tag as shown below.
<CFSET arItems = ArrayNew(1)>
Next we're going to add four methods to the component. The first method is the Add method. The Add method will take two arguments, FirstName and LastName, both string literals. The Add function simply adds an element to the private variable arItems using the intrinsic function, ArrayAppend(). The tricky part is that our Add method needs to add a value that represents an instance of an object. Since we can't use the CFOBJECT tag inside the ArrayAppend() function, we will use the CreateObject() function, shown below. After we add that element to the array, we also need to get the length of the array so we know the index of our recently added user. Again, locking is important here, because we want to add an element to the array and then get the length of the array before anyone else adds another element to it. This is sometimes called a race or race to commit, in database terminology. If we don't lock the actions, we will be racing against other requests to add elements to the array, potentially returning the wrong values to the calling page.
<CFSET ArrayAppend(arItems, CreateObject("component","ActiveUser")>
<CFSET idx = ArrayLen(arItems)>
The next two lines of code in our function will be calling methods from the prebuilt ActiveUser object. These methods set three internal variables in the ActiveUser object: the user's first name, the user's last name, and the date the user logged in.
The last thing we do is return the current element of the array for the programmer to use in the calling page, if necessary. That was the hard part. The next three functions are short and sweet, so I'm going to spend more time describing why you need to do this, rather than stepping through the code line by line. Listing 2 shows the code for the entire collection object.
With the Remove method, we require one argument that is an integer representing the index of the internal array, arItems. We need to check to make sure the value passed is less than or equal to the length of the array so there aren't any errors produced, and then we simply remove that element using the ArrayDeleteAt() function. Remember, you'll need to lock this action to prevent the wrong index of the array from being deleted. In a situation where the method is called twice, there will be a race to commit the deletion. In the event the deletion was not locked, the array would be resized after the first deletion and then the wrong index could potentially be deleted during the second deletion.
The Item method also requires an index value, but the result is different. Instead of removing an item (or doing any type of action), we're just going to return the instance of the ActiveUser object that was stored at that index. This allows us to access each individual object from external ColdFusion templates easily, as you'll see later.
The Count method accepts no arguments and returns an integer describing the number of objects in our collection. We use the ArrayLen() function to determine the return value.
That's it for our collection. All of the internal code is written for our ActiveUsers collection to work properly. It's relatively easy to generate code for collections once you understand the concepts. Now we're going to look at how to use collections in ColdFusion templates.
Making the Collection Persist
In order for our "who's on" application to persist, we need to set up the ActiveUsers collection in the Application scope. Open the Application.cfm file in Listing 3 and add the following code:
<CFIF NOT IsDefined("Application.objActiveUsers")>
<CFOBJECT NAME="Application.objActiveUsers" COMPONENT="ActiveUsers">
This code basically says to check whether the Application.objActiveUsers collection is defined at the beginning of every request. If it isn't defined, it will create the collection using the CFOBJECT tag.
Accessing the Collection
In the index.cfm file (see Listing 4) we're going to output the current number of users online and then loop through the ActiveUsers collection and output data pertaining to the users that are online. You can do all this using the code below:
<CFSET iCount = Application.objActiveUsers.Count()>
As you'll see, we've set the iCount variable to the value of the ActiveUsers collection's Count method. This lets us know how many active users are online right now. Now we can loop through the collection using a simple FROM/TO (or FOR) loop where the TO attribute is equal to the number of users online, or iCount.
We can access the individual objects in the collection using the Item(index) property such as Application.objActiveUsers.Item(i). In the code below, we use that notation to call different methods of the object, such as GetName(), GetLoginTime(), and GetMinutesActive().
<CFLOOP FROM="1" TO="#iCount#" INDEX="i">
<CFSET stName = Application.objActive
#i# - #stName["FirstName"]#
#TimeFormat(Application.objActiveUsers.Item(i).GetLoginTime(), 'h:mm tt')# -
Running index.cfm at this point in time would result in the printing of "Number of Users: 0", since we haven't added any users to the collection. In order to add users to the collection we have to call the Add() method of the ActiveUsers collection. In this example, we'll make a ColdFusion page called AddUser.cfm (see Listing 5) that requires two URL variables called FirstName and LastName. The following code is all we'll use for our AddUser.cfm file:
<CFSET objActiveUser = Application.objActive
If we access the AddUser.cfm page passing "Steve" and "Parks" through the query string such as
our page will then add the user to the collection and refresh us to the index.cfm page. You should now see that there is one user named Steve Parks in the collection. If your browser caches the index.cfm page, you may have to manually refresh the page. In the index.cfm file we called the GetName(), GetLoginTime(), and GetMinutesActive() methods from the ActiveUser object in the collection. You'll now see that data outputted through the collection. Try it again, adding another user using your name. You should now see that you are in the collection as well.
The last file that needs to be created is the RemoveUser.cfm file, which will remove users from the collection. Instead of passing the FirstName or LastName of the user, you'll need to pass a valid index. In this example, we'll just remove the first index, but in theory you would remove users based on an algorithm possibly determined by a method called GetMinutesIdle(). To remove the first user from the application, call the file RemoveUser.cfm, shown in Listing 6, passing a value of 1 in the attribute index, as shown below:
We've now created our ActiveUsers collection in a simplified form. You can add properties and methods to the ActiveUser object to make the system more robust. I recommend adding locking and validation to the Application scope and methods, respectively.
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.
Jan. 26, 2015 12:15 PM EST Reads: 2,208
SYS-CON Media announced that Cisco, a worldwide leader in IT that helps companies seize the opportunities of tomorrow, has launched a new ad campaign in Cloud Computing Journal. The ad campaign, a webcast titled 'Is Your Data Center Ready for the Application Economy?', focuses on the latest data center networking technologies, including SDN or ACI, and how customers are using SDN and ACI in their organizations to achieve business agility. The Cisco webcast is available on-demand.
Jan. 26, 2015 12:00 PM EST Reads: 1,305
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.
Jan. 26, 2015 12:00 PM EST Reads: 7,549
"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.
Jan. 26, 2015 11:30 AM EST Reads: 2,492
“The age of the Internet of Things is upon us,” stated Thomas Svensson, senior vice-president and general manager EMEA, ThingWorx, “and working with forward-thinking companies, such as Elisa, enables us to deploy our leading technology so that customers can profit from complete, end-to-end solutions.” ThingWorx, a PTC® (Nasdaq: PTC) business and Internet of Things (IoT) platform provider, announced on Monday that Elisa, Finnish provider of mobile and fixed broadband subscriptions, will deploy ThingWorx® platform technology to enable a new Elisa IoT service in Finland and Estonia.
Jan. 26, 2015 11:00 AM EST Reads: 1,539
Advanced Persistent Threats (APTs) are increasing at an unprecedented rate. The threat landscape of today is drastically different than just a few years ago. Attacks are much more organized and sophisticated. They are harder to detect and even harder to anticipate. In the foreseeable future it's going to get a whole lot harder. Everything you know today will change. Keeping up with this changing landscape is already a daunting task. Your organization needs to use the latest tools, methods and expertise to guard against those threats. But will that be enough? In the foreseeable future attacks w...
Jan. 26, 2015 11:00 AM EST Reads: 2,898
As enterprises move to all-IP networks and cloud-based applications, communications service providers (CSPs) – facing increased competition from over-the-top providers delivering content via the Internet and independently of CSPs – must be able to offer seamless cloud-based communication and collaboration solutions that can scale for small, midsize, and large enterprises, as well as public sector organizations, in order to keep and grow market share. The latest version of Oracle Communications Unified Communications Suite gives CSPs the capability to do just that. In addition, its integration ...
Jan. 26, 2015 11:00 AM EST Reads: 2,842
Building low-cost wearable devices can enhance the quality of our lives. In his session at Internet of @ThingsExpo, Sai Yamanoor, Embedded Software Engineer at Altschool, provided an example of putting together a small keychain within a $50 budget that educates the user about the air quality in their surroundings. He also provided examples such as building a wearable device that provides transit or recreational information. He then reviewed the resources available to build wearable devices at home including open source hardware, the raw materials required and the options available to power s...
Jan. 26, 2015 11:00 AM EST Reads: 2,027
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...
Jan. 26, 2015 10:45 AM EST Reads: 2,495
From telemedicine to smart cars, digital homes and industrial monitoring, the explosive growth of IoT has created exciting new business opportunities for real time calls and messaging. In his session at @ThingsExpo, Ivelin Ivanov, CEO and Co-Founder of Telestax, shared some of the new revenue sources that IoT created for Restcomm – the open source telephony platform from Telestax. Ivelin Ivanov is a technology entrepreneur who founded Mobicents, an Open Source VoIP Platform, to help create, deploy, and manage applications integrating voice, video and data. He is the co-founder of TeleStax, a...
Jan. 26, 2015 10:45 AM EST Reads: 3,005
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...
Jan. 26, 2015 10:30 AM EST Reads: 2,651
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...
Jan. 26, 2015 10:30 AM EST Reads: 2,322
Disruptive macro trends in technology are impacting and dramatically changing the "art of the possible" relative to supply chain management practices through the innovative use of IoT, cloud, machine learning and Big Data to enable connected ecosystems of engagement. Enterprise informatics can now move beyond point solutions that merely monitor the past and implement integrated enterprise fabrics that enable end-to-end supply chain visibility to improve customer service delivery and optimize supplier management. Learn about enterprise architecture strategies for designing connected systems tha...
Jan. 26, 2015 10:00 AM EST Reads: 2,873
SYS-CON Events announced today that CodeFutures, a leading supplier of database performance tools, has been named a “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. CodeFutures is an independent software vendor focused on providing tools that deliver database performance tools that increase productivity during database development and increase database performance and scalability during production.
Jan. 26, 2015 10:00 AM EST Reads: 1,623
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...
Jan. 26, 2015 10:00 AM EST Reads: 2,119
"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.
Jan. 26, 2015 09:30 AM EST Reads: 2,130
Recurring revenue models are great for driving new business in every market sector, but they are complex and need to be effectively managed to maximize profits. How you handle the range of options for pricing, co-terming and proration will ultimately determine the fate of your bottom line. In his session at 15th Cloud Expo, Brendan O'Brien, Co-founder at Aria Systems, session examined: How time impacts recurring revenue How to effectively handle customer plan changes The range of pricing and packaging options to consider
Jan. 26, 2015 09:00 AM EST Reads: 2,468
Things are being built upon cloud foundations to transform organizations. This CEO Power Panel at 15th Cloud Expo, moderated by Roger Strukhoff, Cloud Expo and @ThingsExpo conference chair, addressed the big issues involving these technologies and, more important, the results they will achieve. Rodney Rogers, chairman and CEO of Virtustream; Brendan O'Brien, co-founder of Aria Systems, Bart Copeland, president and CEO of ActiveState Software; Jim Cowie, chief scientist at Dyn; Dave Wagstaff, VP and chief architect at BSQUARE Corporation; Seth Proctor, CTO of NuoDB, Inc.; and Andris Gailitis, C...
Jan. 26, 2015 09:00 AM EST Reads: 2,495
The Industrial Internet revolution is now underway, enabled by connected machines and billions of devices that communicate and collaborate. The massive amounts of Big Data requiring real-time analysis is flooding legacy IT systems and giving way to cloud environments that can handle the unpredictable workloads. Yet many barriers remain until we can fully realize the opportunities and benefits from the convergence of machines and devices with Big Data and the cloud, including interoperability, data security and privacy.
Jan. 26, 2015 07:45 AM EST Reads: 2,408
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.
Jan. 26, 2015 02:00 AM EST Reads: 2,761