Evaluate

Evaluate(string_expression1 [, string_expression2 [, ... ] ] )

<cfset var=Evaluate("qNames.#colname#[#index#]")>

<!--- This shows the use of DE and Evaluate --->
<h3>Evaluate Example</h3>
<cfif IsDefined("FORM.myExpression")>
<h3>The Expression Result</h3>
<cftry>
<!--- Evaluate the expression --->
<cfset myExpression = Evaluate(FORM.myExpression)>
<!--- Use DE to output the value of the variable, unevaluated --->
<cfoutput>
<I>The value of the expression #Evaluate(DE(FORM.MyExpression))#
is #MyExpression#.</I>
</cfoutput>
...

Comments

halL said on Apr 15, 2004 at 2:35 PM :

The Evaluate function dynamically parses and evaluates an expression at run time. The Evaluate function can increase processing time compared to other techniques of getting dynamic values in ColdFusion because ColdFusion must parse and compile the expression that the function contains at run time, not just compile time.

In many cases you can avoid using the evaluate function by putting variable data and expressions in pound signs in ColdFusion cfoutput regions, or by using the cfset function with an expression.

For example, the following example sets a dynamically named variable without using Evaluate:

<cfset var1= "x">
<cfset "#var1#" = "My value">
<cfoutput>#x#</cfoutput><br>

You use the Evaluate function if you have a variable (var1) that contains the name of a variable (var2), and need to get the value of var2, as in the following example:

<cfset var1="var2">
<cfset var2="3">
<cfoutput>#Evaluate(var1)#</cfoutput>

Evaluate can also be useful in complex cases, where other techniques could result in convoluted code.

For information on the Evaluate function and how you can avoid using it, see http://livedocs.macromedia.com/coldfusion/6.1/htmldocs/exprea29.htm and the pages that follow it. (Click the right arrows at the top or bottom of the page.)

kodemonki said on Jan 4, 2008 at 12:33 PM :

Numbers less than 1 and greater than 0 (I haven't tried less than 0 and greater than -1) must have a leading zero, otherwise evaluate says . is an invalid parser construct.

Hopefully this will save someone a lot of time.

I'm not quite sure how to work around this if you create a string formula from variables stored in a database, since I don't know how to save a number as 0.2 instead of .2 . . .

halL said on Jan 4, 2008 at 12:48 PM :

I haven't tested this in CF 6, but CF 8 does not appear to have this issue.