Adobe 38043740 - ColdFusion Standard - Mac Development Manual page 217

DEVELOPING COLDFUSION 9 APPLICATIONS
Building Blocks of ColdFusion Applications
<cf_getmd Name=#NameYouEntered#>
To pass multiple attributes to a custom tag, separate them with a space in the tag as follows:
<cf_mytag Firstname="Thadeus" Lastname="Jones">
In the custom tag, you use the Attributes scope to access attributes passed to the tag. Therefore, in the getmd.cfm page,
you access the passed attribute as
and
Attributes.Firstname
The custom tag page can also access variables set in the calling page by prefixing the calling page's local variable with
Caller. However, this technique is not the best way to pass information to a custom tag, because each calling page
would be required to create variables with the names required by the custom tag. You can create more flexible custom
tags by passing parameters using attributes.
Variables created within a custom tag are deleted when the processing of the tag terminates. Therefore, if you want to
pass information back to the calling page, write that information back to the Caller scope of the calling page. You
cannot access the custom tag's variables outside the custom tag itself.
For example, use the following code in the getmd.cfm page to set the variable Doctor on the calling page:
<cfset Caller.Doctor="Doctor " & Attributes.Name>
If the variable Doctor does not exist in the calling page, this statement creates it. If the variable exists, the custom tag
overwrites it.
The following image shows the relationship between the variables on the calling page and the custom tag:
<cfset NameYouEntered="Smith">
<cf_getmd Name=#NameYouEntered#>
<cfoutput>
You are now #Variables.Doctor#.<br>
</cfoutput>
A. calling page B. getmd.cfm
One common technique used by custom tags is for the custom tag to take as input an attribute that contains the name
of the variable to use to pass back results. For example, the calling page passes returnHere as the name of the variable
to use to pass back results:
<cf_mytag resultName="returnHere">
In mytag.cfm, the custom tag passes back its results using the following code:
<cfset "Caller.#Attributes.resultName#" = result>
Be careful not to overwrite variables in the calling page from the custom tag. Adopt a naming convention to minimize
the chance of overwriting variables. For example, prefix the returned variable with customtagname_, where
customtagname is the name of the custom tag.
Note: Data that pertains to the HTTP request or to the current application is visible in the custom tag page. This data
includes the variables in the Form, URL, Cgi, Request, Cookies, Server, Application, Session, and Client scopes.
. The mytag.cfm custom tag page refers to the passed attributes as
Attributes.Name
.
Attributes.Lastname
<cfset Caller.Doctor="Doctor " & Attributes.Name>
Last updated 1/20/2012
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