cfdocs

isDefined

Evaluates a string value to determine whether the variable named in it exists.

isDefined(variable_name)

returns boolean

Argument Reference

Name	Type	Required	Default	Description
variable_name	string	Yes		A string expression containing the name of a variable to check the existence of. Only simple dotted notation is supported (for example myVar, arguments.myArg, myStruct.key). Square bracket notation to reference array elements or struct keys is not supported.

Using IsDefined

Checking for the existence of a form variable.

<cfif isDefined("form.submit")>...</cfif>

Scope Evaluation Order and Unscoped Variables

Beware of scope evaluation order when checking for an unscoped variable name.

url.foo = "url.foo" ; form.foo = "form.foo"; writeoutput("Is 'foo' defined? " & isDefined("foo")); writeoutput(isDefined("foo") ? " (" & foo & ")" : "");

Expected Result: Is ‘foo’ defined? YES (url.foo)

Dot-notation Variable Names

Potentially unexpected behavior when checking for a dot-notation variable containing a scope name.

local["form.submit"] = "local['form.submit']" ; form.submit = "form.submit"; writeoutput("Is 'form.submit' defined?" & isDefined("form.submit")); writeoutput(isDefined("form.submit") ? " (" & form.submit & ")" : ""); writeoutput("<br>"); writeoutput("Is 'submit' defined? " & isDefined("submit")); writeoutput(isDefined("submit") ? " (" & submit & ")" : "");

Expected Result: Is ‘form.submit’ defined? YES (local[‘form.submit’]) Is ‘submit’ defined? YES(form.submit)

This site is open source. Improve this page.