| 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. |
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| Returns
True, if the variable is found, or, for a structure, if the specified key is defined; False, otherwise. The return value is 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. |
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| Category
Decision functions |
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Function syntaxIsDefined("variable_name")
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| See also
Evaluate |
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| History
ColdFusion MX: Changed behavior: this function can process only the following constructs:
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| Parameters
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| 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"))
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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">
<input type="Submit" name="">
</form>
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| VARIABLE_NAME | |