MACROMEDIA ColdFusion MX, Develop Manual, Page: 193 / 860

Creating user-defined functions 193
You might call the function with argument names, as follows:
<cfoutput>
Interest: #TotalInterest(principal=Form.Principal, annualPercent=Form.Percent,
months=Form.Months)#
</cfoutput>
Creating user-defined functions
You can use tags or CFScript to create a UDF. Each technique has advantages and disadvantages.
Creating functions using CFScript
You use the
function
statement to define the function in CFScript. CFScript function
definitions have the following features and limitations:
•
The function definition syntax is familiar to anyone who uses JavaScript or most programming
languages.
•
CFScript is efficient for writing business logic, such as expressions and conditional operations.
•
CFScript function definitions cannot include CFML tags.
The following is a CFScript definition for a function that returns a power of 2:
<cfscript>
function twoPower(exponent) {
return 2^exponent;
}
</cfscript>
For more information on how to use CFScript to define a function, see “Defining functions in
CFScript” on page 198 .
Creating functions using tags
You use the
cffunction
tag to define a UDF in CFML. The
cffunction
tag syntax has the
following features and limitations:
•
Developers who have a background in CFML or HTML, but no scripting or programming
experience will be more familiar with the syntax.
•
You can include any ColdFusion tag in your function definition. Therefore, you can create a
function, for example, that accesses a database.
•
You can embed CFScript code inside the function definition.
•
The
cffunction
tag provides attributes that enable you to easily limit the execution of the tag
to authorized users or specify how the function can be accessed.
The following code uses the
cffunction
tag to define the exponentiation function:
<cffunction name="twoPower" output=True>
<cfargument name="exponent">
<cfreturn 2^exponent>
</cffunction>
For more information on how to use the
cffunction
tag to define a function, see “Defining
functions using the cffunction tag” on page 200 .