While ColdFusion does not always allow you to construct a variable name in-line from variable pieces, it does let you to do so in the most common uses, as described in the following sections.

Using number signs to construct a variable name in assignments

You can combine text and variable names to construct a variable name on the left side of a cfset assignment. For example, the following code sets the value of the variable Product12 to the string "Widget":

<cfset ProdNo = 12>
<cfset "Product#ProdNo#" = "Widget">

To construct a variable name this way, all the text on the left side of the equal sign must be in quotation marks.

This usage is less efficient than using arrays. The following example has the same purpose as the previous one, but requires less processing:

<cfset MyArray=ArrayNew(1)>
<cfset prodNo = 12>
<cfset myArray[prodNo] = "Widget">

Dynamic variable limitation

When you use a dynamic variable name in quotation marks on the left side of an assignment, the name must be either a simple variable name or a complex name that uses object.property notation (such as MyStruct.#KeyName#). You cannot use an array as part of a dynamic variable name. For example, the following code generates an error:

<cfset MyArray=ArrayNew(1)>
<cfset productClassNo = 1>
<cfset productItemNo = 9>
<cfset "myArray[#productClassNo##productItemNo#]" = "Widget">

However, you can construct an array index value dynamically from variables without using quotation marks on the left side of an assignment. For example, the preceding sample code works if you replace the final line with the following line:

<cfset myArray[#productClassNo# & #productItemNo#] = "Widget">

Dynamically constructing structure references

The ability to use associative array notation to reference structures provides a way for you to use variables to dynamically create structure references. (For a description of associative array notation, see Structure notation.) Associative array structure notation allows you to use a ColdFusion expression inside the index brackets. For example, if you have a productName structure with keys of the form product_1, product_2 and so on, you can use the following code to display the value of productName.product_3:

<cfset prodNo = 3>
<cfoutput>
    Product_3 Name: #ProductName["product_" & prodNo]#
<cfoutput>

For an example of using this format to manage a shopping cart, see Example: a dynamic shopping cart.