Tests for a parameter's existence, tests its data type, and, if a default value is not assigned, provides one.
<cfparam name = "param_name" type = "data_type" default = "value">
cfcookie,
cfregistry,
cfsavecontent,
cfschedule,
cfset
Attribute | Req/Opt | Default | Description |
---|---|---|---|
name |
Required |
|
Name of parameter to test (such as "Client.Email " or "Cookie.BackgroundColor "). If omitted, and if the parameter does not exist, an error is thrown. |
type |
Optional |
|
|
default |
Optional |
|
Value to set parameter to if it does not exist. |
You can use this tag to make the following tests:
name
attribute. If it does not exist, ColdFusion Server stops processing the page and returns an error.
name
and type
attributes. If the variable of the specified type does not exist, ColdFusion returns an error. name
and default
attributes. If it does not exist, it is created and set to the value of the default
attribute. If it exists, processing continues; the value is not changed. <!--- 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 thata 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 ---> <cfif tempVar is not #StoreTempVar# and tempVar is not ""> <h3>The value of tempVar has changed: the new value is <cfoutput>#tempVar#</cfoutput></h3> </cfif> <p> <form action = "cfparam.cfm" method = "post"> Type in a new value for tempVar, and hit submit:<br> <input type = "Text" name = "tempVar"> <input type = "Submit" name = "" value = "submit"> </form>