User Guide
cfparam 327
Usage
You can use this tag to make the following tests:
• To test whether a required variable exists, use this tag with only the name attribute. If it does
not exist, ColdFusion MX stops processing the page and returns an error.
• To test whether a required variable exists, and that it is of the specified type, use this tag with
the
name and type attributes. If the variable does not exist or its value is not of the specified
type, ColdFusion returns an error.
• To set a default value for the variable, use this tag with the name and default attributes. If the
variable does not exist, it is created and set to the
default attribute value. If the variable exists,
processing continues; the value is not changed.
If you specify
variableName for the type attribute, the parameter’s value must be a string that is
in ColdFusion variable name format; that is, starts with a letter, underscore (_), or Unicode
currency symbol, and contains letters, numbers, underscores, periods, and Unicode currency
symbols, only. ColdFusion does not check whether the parameter value corresponds to an existing
ColdFusion variable.
Tip: To improve performance, avoid using the cfparam tag in ColdFusion functions, including in CFC
methods. Instead, place the
cfparam tags in the body of the CFML pages.
Example
<!--- This example shows how to use CFPARAM to define default values for page
variables. -------->
<cfparam name = "storeTempVar" default = "my default value">
<cfparam name = "tempVar" default = "my default value">
<!--- Check if form.tempVar was passed. --->
<cfif IsDefined("form.tempVar") is "True">
<!--- Check if form.tempVar is not blank. --->
<cfif form.tempVar is not "">
<!--- If not, set tempVar to value of form.tempVar --->
<cfset tempVar = form.tempVar>
</cfif>
</cfif>
<body>
<h3>cfparam Example</h3>
<p>cfparam is used to set default values so that a developer does not have to
check for the existence of a variable using a function like IsDefined.
<p>The default value of our tempVar is
"<cfoutput>#StoreTempVar# </cfoutput>"
<!--- Check if tempVar is still the same as StoreTempVar.
and that tempVar is not blank --->
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.
Attribute Req/Opt Default Description