Webmaster Forum / ColdFusion / Advanced Techniques / August 2005

"Am I understanding you right in that you're instantiating the object in the
session scope, and then trying to post to it using the "?method=add" url query
param? If, so, I don't think that will work, because you're not posting to the
session object, but rather a new instance of it."

Yes, of course! Thank you for clearing that up.

Your suggested workaround #1 is what I was wanting to avoid. I'd never tried
to implement CFC methods via the query string before, so I wanted to try that,
but also any sort of handler page would be so small I wanted to avoid it.

I agree that #2 is bad design. This project is already impure enough, with
CFCs referencing properties and config values in the request scope.

I'm gettin' there... ;)

Okay, I've moved the access to a 'helper' page as suggested.

However, now I'm getting type errors I don't follow. This 'cart' of mine holds
a single value which is a single-dimension array. On the CFCs init() method, I
initialize that value:

variables.coupons = arrayNew(1);

Later, the add() and delete() methods use a helper method, getMyCoupons(), to
get the current value of #variables.coupons# at any time.

The CFC init()s fine, but the first attempt to call getMyCoupons() throws an
exception saying the value returned is not of type array.

Attached is the updated CFC code. I can post the 'helper page' code if
necessary, though I don't know if it's relevant.

<CFcomponent>
   
    <CFfunction name="init" output="false" returntype="coupon-book">
        <CFscript>
            variables.coupons = arrayNew(1);
            return this;           
        </CFscript>
    </CFfunction>
   
    <CFfunction name="getMyCoupons" output="false" returntype="array">
        <CFreturn variables.coupons>
    </CFfunction>
   
    <CFfunction name="add" output="false" returntype="void">
        <CFargument name="id" type="numeric" required="yes">
        <CFscript>
            var arrayList = arrayToList(getMyCoupons());
            if (not listFind(arrayList,arguments.id)) {
                variables.coupons = arrayAppend(variables.coupons,arguments.id);
            }
        </CFscript>
        <CFlocation url="#cgi.http_referer#" addtoken="no">
    </CFfunction>
   
    <CFfunction name="delete" output="false" returntype="void">
        <CFargument name="id" type="numeric" required="yes">
        <CFscript>
        var currentCoupons = getMyCoupons();
        for (i=1; i lt arrayLen(currentCoupons); i=i+1) {
            if (arguments.id is i) {
                variables.coupons = arrayDeleteAt(variables.coupons,i);
            }
        }
        </CFscript>
        <CFlocation url="#cgi.http_referer#" addtoken="no">
    </CFfunction>
   
</CFcomponent>

The main view template receives a request like:

?action=add&coupon=3

Based on the action param, a method is called in the coupon-book. The error
WAS being thrown from the module invoked at the end of the attached code. I
reworked some things, and now no error is being thrown, but nothing is being
added to the array. I know it's hitting the method call because it is
redirecting back to the referer. I also did a CFabort in the method call to
make sure.

<CFparam name="url.action" default="">
<CFparam name="url.coupon" default="0">

<CFif not isNumeric(url.coupon) or url.coupon lt 0>
    <CFset url.action = ''>
</CFif>

<CFswitch expression="#url.action#">
    <CFcase value="add">
        <CFset session.couponBook.add(url.coupon)>
    </CFcase>
    <CFcase value="delete">
        <CFset session.couponBook.delete(url.coupon)>
    </CFcase>
</CFswitch>

<CFmodule
    template="/system/taglibs/coupons/coupon-book.cfm"
    standalone="true"

Just two things.

1) For better or worse, I have the "I started, so I'll finish"  mentality.
I wouldn't do

<CFlocation url="#cgi.http_referer#" addtoken="no">

just before the finish-line, </cffunction>. Instead, I would cflocate
on the cfm page that invokes the cfc, giving the function the opportunity to
finish gracefully.

2) I find this construction, a recursive instantiation of a component within
itself, unnecessarily complicated:

<CFcomponent>
<CFfunction name="init" output="false" returntype="coupon-book">
<CFscript>
variables.coupons = arrayNew(1);
return this;           
</CFscript>
</CFfunction>
...
...etc.

I would replace this excerpt with

<CFcomponent>
<cfset variables.coupons = arrayNew(1)>

Wherever you need to have an instance of the component, you only have to
create an object, outside the component itself, the way BSterner does.

Good luck.