Adobe COLDFUSION 9 Manual page 79

Developing applications

Hide thumbs Also See for COLDFUSION 9:

Table of Contents

DEVELOPING COLDFUSION 9 APPLICATIONS

The CFML Programming Language

This does not mean that you must always avoid dynamic evaluation. However, given the substantial performance costs

of dynamic evaluation, first ensure that one of the following techniques cannot serve your purpose:

• An array (using index variables)

• Associative array references containing expressions to access structure elements

• Dynamically generated variable names

Dynamic variable naming without dynamic evaluation

While ColdFusion does not always allow you to construct a variable name inline from variable pieces, but it does allow

the most common uses.

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

example, the following code sets the value of the variable Product12 to the string "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:

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:

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:

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

page 93.) 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:

Product_3 Name: #ProductName["product_" & prodNo]#

For an example of using this format to manage a shopping cart, see

"Example: a dynamic shopping

Last updated 8/5/2010

assignment. For

notation" on

cart" on page 79.