User Guide

Understanding conditional processing 27

You use conditional processing to customize the behavior of your application. Conditional

processing facilitates decision making and lets you control how the code on a page is processed.

In ColdFusion, you implement conditional processing with flow control tags. These tags are

similar to other programming language control elements, such as

if, then, and else.

Conditional processing tags

ColdFusion provides several tags that let you control how a page is processed. When using these

tags, you can facilitate decision making in your code. The most fundamental tags used to control

code execution are the

cfif, cfelse, and cfelseif tags. Because you will see and use these

tags in Part II of this book, the following sections provide a basic introduction on how to use

these tags. For more information about other conditional processing tags, including tags for

looping, see Developing ColdFusion MX Applications.

Using cfif to evaluate True or False conditions

To create statements that let you evaluate conditions and perform an action based on the result,

you use the

cfif tag to create a cfif statement. The basic syntax is as follows:

HTML and CFML tags executed if expression is True.

</cfif>

In the previous example, ColdFusion only executes the code inside the cfif statement if the

expression evaluates to True. To perform actions if the expression is False, you can use the

cfelse

tag. For example, if the following

cfif expression evaluates to False, then the code between the

cfelse tag and the cfif tag is processed:

HTML and CFML tags executed if expression is True.

HTML and CFML tags executed if expression is False.

</cfif>

Using cfelseif to evaluate multiple expressions

To evaluate multiple expressions in a cfif statement, you can use cfelseif and cfelse in your

statement; for example:

HTML and CFML tags executed if expression 1 is True.

HTML and CFML tags executed if expression 2 is True.

HTML and CFML tags executed for expression(s) that is False.

</cfif>

The following example shows you how you can evaluate multiple expressions using these tags. In

this example, you created a form in which users can enter their state to determine their state tax:

#form.state# State Tax: 8.5%

#form.state# State Tax: 8.2%

#form.state# State Tax Unknown

</cfif>

</cfoutput>