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

Making Decisions in Your Code with ColdFusion "cfif"

Before you can implement conditional logic in your code you have to understand what conditional logic is

This month I will examine the cfif tag and discuss how we can use that tag to make decisions in our code. Along the way I'll talk about Boolean logic, decision operators, and Boolean operators in CFML.

Understanding Conditional Logic
Before you can implement conditional logic in your code you have to understand what conditional logic is. I have no doubt that every one of you knows what conditional logic is, although you may never have heard it referred to as such. Conditional logic is just a fancy way of saying that you are going to make a decision. Usually the decision is based upon some sort of condition or the result of an operation.

You and I make decisions every day, so let's delve into some real-world examples. Suppose I'm driving a car and come to an intersection with another road. I need to make a decision whether to turn left, turn right, or continue straight on the main road. Each decision may have different consequences. If I turn right, I go to the bank. If I turn left, I go to the grocery store. Going straight might take me somewhere else, home, for example. Since it has been a long day, I want to go home. I'm going to drive straight. This is an example of conditional logic in practice. I made a choice to go straight, based on a condition, I want to go home, and something happened as a result of that condition.

Making decisions about groceries and the bank is all well and good, but how does this apply to Web development? I'm glad you asked. Suppose you have a sign-up form on your Web site. Your users enter some account information, such as an e-mail address, their name, a username, and password. You take that information and create a user account in your database.

What happens if the user does not enter a username? Can you still create the account? How do you handle that situation? You can use conditional logic to make sure that the username is not left blank. Suppose a user looks at the shopping cart before adding items to it? You can use conditional logic to display an "empty cart" message. Suppose a user enters a birth date as November 15, 2050? You get the idea - we can use conditional logic in our code to solve these types of problems.

The Format of the cfif Tag
In CFML, you can use the cfif tag to perform conditional logic statements. It comes in this format:

<cfif expression>
Perform Actions

The cfif tag is an oddball tag in the CFML language. Unlike most tags, it doesn't take any explicit parameter name and value arguments; it is simply followed by an expression after the tag name. A review of expressions can be found in last month's article; or you can go straight to the source: http://livedocs.macromedia.com/coldfusion/6.1/htmldocs/cfml_b14.htm. The CFML interpreter uses an expression to determine whether or not to process data. Expressions are literal values, variables, or functions (which return a Boolean value).

The expression inside the cfif tag must evaluate to a Boolean value (a true/false). Boolean values are represented as either "true" or "false", "yes" or "no", or "0" or any number. If the expression evaluates to true, then the action immediately following the <cfif> is performed. If the expression evaluates to false, then the action is not performed and template execution will continue after the end cfif tag. There are two types of operators that are used with cfif tags: decision operators and Boolean operators. Both evaluate to Boolean values.

Decision and Boolean Operators
The two types of operators used in a cfif expression are decision operators and Boolean operators. Boolean operators refer to specific operators from Boolean algebra. Decision operators are used for comparisons. This is a list of the Boolean and decision operators supported in CFML:

  • NOT: A Boolean operator that returns the opposite of the specified expressions. If you want the NOT of true, then you get false. The NOT of false is true.
  • AND: A Boolean operator that returns true if both operands are true, but false otherwise.
  • OR: A Boolean operator that returns true if at least one of the operands is true, but returns false otherwise.
  • XOR: A Boolean operator that performs an exclusive or. If only one of the values is true, then the result is true. Otherwise the result is false.
  • EQV: A Boolean operator that performs equivalence. Returns true if both operands are true or both operands are false. Returns false if the operands are different.
  • IMP: A Boolean operator that performs implication. It is akin to the logical statement "If condition 1, then condition 2." This returns false if condition 1 is true and condition 2 is false. True is returned in all other cases.
  • IS, EQUAL, EQ: Decision operators that test for two values being equal. If the first value is equal to the second value, the final result is true.
  • IS NOT, NOT EQUAL, NEQ: Decision operators that test for two values not being equal. If the two values are equal, then the final result will be false.
  • GREATER THAN, GT: Decision operators that are used to check if the first value is greater than the second value.
  • GREATER THAN OR EQUAL TO, GTE, GE: Decision operators that check to see if the first value is larger than or equal to the second value.
  • LESS THAN, LT: Decision operators that are used to check if the first value is smaller than the second value.
  • LESS THAN OR EQUAL TO, LTE, LE: Decision operators that check to see if the first value is smaller than or equal to the second value.
  • CONTAINS: A decision operator that returns true if the value on the left contains the value on the right.
  • DOES NOT CONTAIN: A decision operator that returns true if the value on the left does not contain the value on the right.

You can read more about decision operators in the Macromedia Livedocs at http://livedocs.macromedia.com/coldfusion/6.1/htmldocs/expresa6.htm and about Boolean operators at http://livedocs.macromedia.com/coldfusion/6.1/htmldocs/expresa5.htm.

It is worth noting the order in which these operations are applied. This builds right off the order of operations I discussed in last month's article. First, the arithmetic operators are applied, and then the string operator is applied. Following that, the decision operators are applied: EQ, NEQ, LT, LTE, GT, GTE, CONTAINS, DOES NOT CONTAIN from left to right in the order that they appear. Then come the Boolean operators. First the NOT operator is applied, then the AND operator. Then the OR operator, followed by the XOR operator. Next comes EQV, and finally, IMP. You can always use parentheses to change the order of operations. In fact, when in doubt, use parentheses to force the order of operations! In most cases you won't be mixing arithmetic or string operands with decision or Boolean ones; however, decision and Boolean operands are often used together. Let me show you how to put this into practice.

Take Some Code for a Test Drive
Suppose you want to make a simple interface for users to choose which way to turn their car. This sample uses an HTML form to collect the user input, as shown below. If you are unfamiliar with HTML forms, I found some great Web-based tutorials located at www.weballey.net/forms and www.wdvl.com/Authoring/Scripting/Tutorial/html_forms_intro.html.

<form action="Go.cfm" method="post">
<input type="Radio" name="Route" value="Right">Right
<input type="Radio" name="Route" value="Left">Left
<input type="Radio" name="Route" value="Straight">Straight<Br>
<input type="submit">

The form uses radio buttons to let the user select a direction and then click Submit to see the result page:

<cfif Route is "Right">
Go to Bank<br>
<cfif Route is "Left">
Go to Store<br>
<cfif Route is "Straight">
Go Home<br>

If you copy this code to see the example in action, make sure that you put it in a file named go.cfm and put both files in the same directory. This code uses the decision operator IS to determine the value of Route. It uses multiple cfif tags to figure out the value of the Route variable and what it should be.

Specifying Additional Conditions with cfelse and cfelseif
Up to this point the cfif tags have performed actions only if an expression resulted to true. What happens when you need to perform some actions when a condition is false? Well, you could use the NOT operator to create a second cfif statement, but there is a better way. CFML offers us the <cfelse> tag. This is the syntax:

<cfif expression>
Perform Actions
Perform Other Actions

The cfif tag remains the same, as do the actions that we perform if the condition is true. What changes is that we have a cfelse tag. The cfelse tag does not take any parameters or expressions - it simply offers the alternative code to run in case a cfif evaluates to false.

If you go back to the driving example, you will see that we have three separate conditions. Turning left directs us to the grocery store, turning right takes us to the bank, and going straight sends us home. In this case, it won't be possible to perform all of the actions at once. Our first example is inefficient because we evaluate all conditions even after finding the correct one.

There is a better way to handle this situation - through the use of a tag called cfelseif. The cfelseif tag allows us to add multiple conditions to our cfif statement. If the first condition does not evaluate to true, then the second cfelseif condition is evaluated. If the second is not true, then the third is evaluated. Use of the cfelseif is optional, and there is no limit to the number of cfelseif conditions you can have. By contrast, the cfelse tag can be used only once. This is the syntax for cfelseif:

<cfif expression>
Perform Actions
<cfelseif expression2>
Perform Other Actions

The code is very similar to the previous sample. The cfelseif tag contains an additional expression, whereas the cfelse did not. It will be evaluated only if the cfif expression is false. When there are cfelseif tags and a cfelse tag, the cfelse tag must always come last (after all cfelseif tags). The previous example used multiple cfif tags. The cfelseif tag lets us combine the separate cfif tags into a single login. This is the code:

<cfif Route is "Right">
Go to Bank<br>
<cfelseif Route is "Left">
Go to Store<br>
Go Home<br>

If the route chosen is right, then we go to the bank. If the route is left we go to the store. If nothing else, we continue to go straight on home.

Where Do I Go from Here?
The cfif statement can get very complicated if you start using one cfif statement inside another cfif statement. If you want to do some independent study, I would suggest reading up on cfswitch at http://livedocs.macromedia.com/coldfusion/ 6.1/htmldocs/tags-c10.htm#wp1103819 and cfcase at http://livedocs.macromedia.com/coldfusion/ 6.1/htmldocs/tags-pa9.htm#wp2664410. They are used together to form case statements, which are a different form of conditionals that you can use in your code. The use of cfswitch and cfcase statements is often a great way to simplify complex cfif.

It has been a pleasure writing these articles for you, and I'm pleased to announce that I've received my first topic request. Next month I will be writing about structures and arrays. Keep the ideas coming!

More Stories By Jeffry Houser

Jeffry is a technical entrepreneur with over 10 years of making the web work for you. Lately Jeffry has been cooped up in his cave building the first in a line of easy to use interface components for Flex Developers at www.flextras.com . He has a Computer Science degree from the days before business met the Internet and owns DotComIt, an Adobe Solutions Partner specializing in Rich Internet Applications. Jeffry is an Adobe Community Expert and produces The Flex Show, a podcast that includes expert interviews and screencast tutorials. Jeffry is also co-manager of the Hartford CT Adobe User Group, author of three ColdFusion books and over 30 articles, and has spoken at various events all over the US. In his spare time he is a musician, old school adventure game aficionado, and recording engineer. He also owns a Wii. You can read his blog at www.jeffryhouser.com, check out his podcast at www.theflexshow.com or check out his company at www.dot-com-it.com.

Comments (7)

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
Every organization is facing their own Digital Transformation as they attempt to stay ahead of the competition, or worse, just keep up. Each new opportunity, whether embracing machine learning, IoT, or a cloud migration, seems to bring new development, deployment, and management models. The results are more diverse and federated computing models than any time in our history.
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...
Japan DX Pavilion at @CloudEXPO Silicon Valley
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, discussed how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team at D...
The graph represents a network of 1,329 Twitter users whose recent tweets contained "#DevOps", or who were replied to or mentioned in those tweets, taken from a data set limited to a maximum of 18,000 tweets. The network was obtained from Twitter on Thursday, 10 January 2019 at 23:50 UTC. The tweets in the network were tweeted over the 7-hour, 6-minute period from Thursday, 10 January 2019 at 16:29 UTC to Thursday, 10 January 2019 at 23:36 UTC. Additional tweets that were mentioned in this...
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...
Where many organizations get into trouble, however, is that they try to have a broad and deep knowledge in each of these areas. This is a huge blow to an organization's productivity. By automating or outsourcing some of these pieces, such as databases, infrastructure, and networks, your team can instead focus on development, testing, and deployment. Further, organizations that focus their attention on these areas can eventually move to a test-driven development structure that condenses several l...
The term "digital transformation" (DX) is being used by everyone for just about any company initiative that involves technology, the web, ecommerce, software, or even customer experience. While the term has certainly turned into a buzzword with a lot of hype, the transition to a more connected, digital world is real and comes with real challenges. In his opening keynote, Four Essentials To Become DX Hero Status Now, Jonathan Hoppe, Co-Founder and CTO of Total Uptime Technologies, shared that ...
Over the course of two days, in addition to insightful conversations and presentations delving into the industry's current pressing challenges, there was considerable buzz about digital transformation and how it is enabling global enterprises to accelerate business growth. Blockchain has been a term that people hear but don't quite understand. The most common myths about blockchain include the assumption that it is private, or that there is only one blockchain, and the idea that blockchain is...
Never mind that we might not know what the future holds for cryptocurrencies and how much values will fluctuate or even how the process of mining a coin could cost as much as the value of the coin itself - cryptocurrency mining is a hot industry and shows no signs of slowing down. However, energy consumption to mine cryptocurrency is one of the biggest issues facing this industry. Burning huge amounts of electricity isn't incidental to cryptocurrency, it's basically embedded in the core of "mini...