MACROMEDIA COLDFUSION 4.5-CFML LANGUAGE Manuel d'utilisateur télécharger pdf (Page 35)

35Writing CFX Tags with Visual C++

5. Leave the Procedure ﬁeld set to ProcessTagRequest unless you changed the name of the

ProcessTagRequest() function produced by the ColdFusion Tag Wizard when you

created your project’s workspace.

6. Leave the Keep Library Loaded unless your DLL will occupy a large amount of space in

the server’s memory and will be used infrequently. Another reason to uncheck this box is

if your DLL is not thread safe. See the “Using CFX Tags Safely: Locking and Thread

Safety” section later in this chapter for details.

7. If you wish, ﬁll in the optional Description ﬁeld.

8. Press OK to register the tag. It will now appear in the list of registered tags in the CFX

Tags page, and is ready for use in your ColdFusion pages.

Using the New Tag

Listing 30.7 shows how the new <CFX_ComputeStandardDeviation> tag can be used in a ColdFusion

page. First, data from the Films table is retrieved using an ordinary

SELECT query. Then the CFX

tag is called, specifying the RatingID column of the query as the column for which to compute the

standard deviation. After the tag executes, the computed standard deviation will be available to

ColdFusion in the

FilmsStdDev variable. Similar steps are used to compute the standard deviation of

the prices in the Merchandise table.

Listing 30.7 ComputeStandardDeviationDemo.cfm—Computing the Standard Deviation

<!---

Filename: ComputeStandardDeviationDemo.cfm

Author: Nate Weiss (NMW)

Purpose: Computes standard deviations

Figure 30.9

Like Java CFX tags,

tags written in C++

need to be registered

in the ColdFusion

Administrator.

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MACROMEDIA COLDFUSION 4.5-CFML LANGUAGE Manuel d'utilisateur Page 35