IsDefined
533
IsDefined
Description
Evaluates a string value to determine whether the variable named in it exists.
This function is an alternative to the
ParameterExists
function, which is deprecated.
Returns
True, if the variable is found, or, for a structure, if the specified key is defined; False, otherwise.
Returns False for an array or structure element referenced using bracket notation. For example,
IsDefined("myArray[3]")
always returns False, even if the array element
myArray[3]
has a
value.
Category
Decision functions
Function syntax
IsDefined
("
variable_name
")
See also
Evaluate
History
ColdFusion MX: Changed behavior: this function can process only the following constructs:
•
a simple variable
•
a named variable with dot notation
•
a named structure with dot notation (for example:
mystruct.key
)
Parameters
Usage
When working with scopes that ColdFusion exposes as structures, the
StructKeyExists
function can sometimes replace this
function. The following lines are equivalent:
if(isDefined("form.myVariable"))
if(structKeyExists(form,"myVariable"))
Example
<cfif IsDefined("form.myString")>
<p>The variable form.myString has been defined, so show its contents.
This construction allows us to place a form and its resulting action code
on the same page and use IsDefined to control the flow of execution.</p>
<p>The value of "form.myString" is <b><i>
<cfoutput>#form.myString#</cfoutput></i></b>
<cfelse>
<p>During the first time through this template, the variable "form.myString"
has not yet been defined, so we do not try to evaluate it.
</cfif>
<form action="#CGI.Script_Name" method="POST">
<input type="Text" name="MyString" value="My sample value">
Parameter
Description
variable_name
String, enclosed in quotation marks. Name of variable to test for.
Summary of Contents for COLDFUSION MX 61-CFML
Page 1: ...CFML Reference...
Page 16: ...16 Contents...
Page 32: ...32 Chapter 1 Reserved Words and Variables...
Page 160: ...160 Chapter 2 ColdFusion Tags html...
Page 245: ...cfmail 245 p input type Submit name form...
Page 299: ...cfreturn 299 cffunction cfcomponent...
Page 354: ...354 Chapter 2 ColdFusion Tags cfoutput cfcatch cftry...
Page 357: ...cfupdate 357 cftable cfif body html...
Page 362: ...362 Chapter 2 ColdFusion Tags cfloop MyDoc cfxml cfdump var MyDoc...
Page 397: ...ASin 397 br input type Text name sinNum size 25 p input type Submit name input type RESET form...
Page 486: ...486 Chapter 3 ColdFusion Functions input type Submit NAME form...
Page 492: ...492 Chapter 3 ColdFusion Functions b http_content x content b cfoutput...
Page 504: ...504 Chapter 3 ColdFusion Functions tr table form...
Page 519: ...IIf 519 cfoutput b...
Page 534: ...534 Chapter 3 ColdFusion Functions input type Submit name form...
Page 542: ...542 Chapter 3 ColdFusion Functions cfif cfif...
Page 547: ...IsStruct 547 cfcase cfswitch...
Page 550: ...550 Chapter 3 ColdFusion Functions IsWDDX returns IsWDDX packet br cfoutput...
Page 559: ...Left 559 option value 9 9 select input type Submit name Remove characters form...
Page 620: ...620 Chapter 3 ColdFusion Functions cfoutput cfloop...
Page 681: ...SetVariable 681 p Your variable varName p The value of varName is varNameValue cfoutput cfif...
Page 724: ...724 Chapter 3 ColdFusion Functions cfelse h3 Conversion error h3 cfif...
Page 743: ...XmlNew 743 cfscript cfdump var MyDoc...
Page 786: ...786 Chapter 5 ColdFusion Java CFX Reference...
Page 798: ...798 Chapter 6 WDDX JavaScript Objects...
Page 806: ...806 Chapter 7 ColdFusion ActionScript Functions...