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.

To determine whether a specific key exists in a structure, use the StructKeyExists function, as follows:

StructKeyExists(structure_name, "key_name")

Do not place the name of the structure in quotation marks, but you do place 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 place 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 theLastName field of the query. 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")>

However, if the key is dynamic, or contains special characters, use the StructKeyExists function.

To get a list of the keys in a CFML structure, you use the StructKeyList function, as follows:

<cfset temp=StructKeyList(structure_name, [delimiter])>

You can specify any character as the delimiter; the default is a comma.

Use the StructKeyArray function to returns an array of keys in a structure, as follows:

<cfset temp=StructKeyArray(structure_name)>