MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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118 Chapter 5: Using Arrays and Structures
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 quotes. 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 ")>
However, if the key is dynamic, or contains special characters, you must use the
StructKeyExists
function.
Note: Using StructKeyExists to test for the existence of a structure entry is more efficient than
using IsDefined . ColdFusion scopes are available as structures and you can improve efficiency by
using
StructKeyExists
to test for the existence of variables.
Getting a list of keys in a structure
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 )>
Note: The StructKeyList and StructKeyArray functions do not return keys in any particular
order. Use the
ListSort
or
ArraySort
functions to sort the results.