Variables

Parameters#

Attribute	Description
name	(Required) Name of the parameter/variable.
default	(Optional) Value to set parameter to if it does not exist.
max	(Optional) The maximum valid value; used only for range validation.
min	(Optional) The minimum valid value; used only for range validation.
pattern	(Optional) A JavaScript regular expression that the parameter must match; used only for regex or regular_expression validation.
type	(Optional) The valid format for the data.
## Using cfset
You can set a ColdFusion variable using the `<cfset>` tag. To output the variable, you need to surround the variable name with hash `#` symbols and enclose it within `<cfoutput>` tags.

<cfset variablename="World!">
<cfoutput>
    Hello #variablename#
</cfoutput>

Using cfparam

The <cfparam> tag creates a variable if it does not already exist. You can assign a default value using the default attribute. This can be used if you want to create a variable, but don’t want to overwrite it if it has been previously created elsewhere.

Here the variable hasn’t been set previously, so it will be assigned with the <cfparam> tag.

<cfparam name="firstName" default="Justin">
<cfoutput>
    Hello #firstName#
</cfoutput>

Here the variable has already been assigned using the <cfset> tag, so this value will override the default value in the <cfparam> tag.

<cfset firstname="Justin">

<cfparam name="firstName" default="Barney">
<cfoutput>
    Hello #firstName#
</cfoutput>

Checking if a Variable Exists

You can check if a variable has been defined in a scope by using ColdFusion’s built in StructKeyExists() function. This can be used inside a <cfif> tag to prevent error messages in the event you attempt to refer to a variable that does not exist. You can also use this function to determine whether a user has performed a certain action or not. The syntax for the function is

StructKeyExists(structure, "key")

The following example checks if the variable firstName exists in the variables scope.

<cfif StructKeyExists(variables, "firstName")>
    Hello #variables.firstname#!
<cfelse>
    Hello stranger!
</cfif>

Alternatively, you may use the function:

isDefined("scopeName.varName")

To avoid ambiguity, it is recommended to declare the scope. For example, If you have a variable in the scope test

<cfset test.name = "Tracy" />

and you test for name in the global scope, you will get a result of true.

isDefined("name") <!--- true --->
isDefined("x.name") <!--- false--->
isDefined("test.name") <!--- true --->

Setting a variable scope

It is a common practice to set application variables to an object scope. This keeps them easy to identify and distinguish from variables in other scopes.

The Variables scope in a CFC is private to the CFC. When you set variables in this scope, they cannot be seen by pages that invoke the CFC.

<cfparam name="variables.firstName" default="Timmy">
<cfset variables.firstName="Justin">

Scopes shared with the calling page include: Form, URL, Request, CGI, Cookie, Client, Session, Application, Server, and Flash. Variables in these scopes are also available to all pages that are included by a CFC.

CFC:

<cfset url.sessionId="23b5ly17">

<cfinclude template="check_session.cfm">

check_session.cfm

<cfif url.sessionId eq "23b5ly17">
    <p>Welcome back!</p>
</cfif>