User Guide

Creating and using structures 113
Getting information about structures and keys
The following sections describe how to use ColdFusion functions to find information about
structures and their keys.
Getting information about structures
To find out if a given value represents a structure, use the
IsStruct function, as follows:
IsStruct(variable)
This function returns True if variable is a ColdFusion structure. (It also returns True if variable is
a Java object that implements the java.util.Map interface.)
Structures are not indexed numerically, so to find out how many name-value pairs exist in a
structure, use the
StructCount function, as in the following example:
StructCount(employee)
To discover whether a specific Structure contains data, use the StructIsEmpty function, as
follows:
StructIsEmpty(structure_name)
This function returns True if the structure is empty, and False if it contains data.
Finding a specific key and its value
To determine whether a specific key exists in a structure, use the
StructKeyExists function, as
follows:
StructKeyExists(structure_name, "key_name")
Do not put the name of the structure in quotation marks, but you do put the key name in
quotation marks. For example, the following code displays the value of the MyStruct.MyKey only
if it exists:
<cfif StructKeyExists(myStruct, "myKey")>
<cfoutput> #mystruct.myKey#</cfoutput><br>
</cfif>
You can use the StructKeyExists function to dynamically test for keys by using a variable to
represent the key name. In this case, you do not put the variable in quotation marks. For example,
the following code loops through the records of the GetEmployees query and tests the myStruct
structure for a key that matches the query’s LastName field. If ColdFusion finds a matching key, it
displays the Last Name from the query and the corresponding entry in the structure.
<cfloop query="GetEmployees">
<cfif StructKeyExists(myStruct, LastName)>
<cfoutput>#LastName#: #mystruct[LastName]#</cfoutput><br>
</cfif>
</cfloop>
If the name of the key is known in advance, you can also use the ColdFusion IsDefined
function, as follows:
IsDefined("structure_name.key")>