Coldfusion 8: IsDefined('URL.variable') and is not ""?

Question

I'm trying to find out if a url variable exists, and if it doesn't, make sure that it's not empty.

This does not work:

<cfif IsDefined('URL.affiliateId') and is not "">
    //
</cfif>

Sportsman

All answers below work, but FYI structKeyExists() is more efficient then isDefined(), and len() is more efficient then NEQ "". Trim() is optional but not a bad idea to include that. – Allpurpose

I think a better reason to use structKeyExists() is accuracy. IsDefined() has a slightly broader scope, which may occasionally lead to unexpected results. – Postmeridian

Answer 1

<cfif structKeyExists(url, 'affiliateID') and trim(url.affiliateID) neq "">...</cfif>

Recovery

Ah, much better. (I am always amazed how many ways you can write this kind of thing ;-) – Postmeridian

Also it's been proven the sturctKeyExists is more efficient than IsDefined. – Ketose

Just so you know why StructKeyExists is more efficient; StructKeyExists() looks for a single variable in a single structure. isDefined() will scan every scope in a prescribed order until it find the variable, even if you specify the scope for the variable in the function call. eg. isDefined("session.userid") will still scan the variables, URL, Form etc scopes until it finds it in the session scope. – Hideandseek

Answer 2

You can simplify the logic a bit as well by using <cfparam> to ensure that the URL variable always exists. Then rather than having 2 conditions, you just need 1.

<cfparam name="URL.affiliateId" type="string" default="" />

<cfif trim( URL.affiliateId ) is not "">
     do stuff here
</cfif>

Spline

True. If the variable's existence does not negatively effect existing code (I was not sure), then cfparam can simplify things – Postmeridian

Answer 3

To ignore most white space

<cfif IsDefined('URL.affiliateId') and len(trim(URL.affiliateId))>
    value is defined and not empty
</cfif>

... or alternately

<cfif IsDefined('URL.affiliateId') and len(trim(URL.affiliateId)) gt 0>
    value is defined and not empty
</cfif>

Postmeridian

Answer 4

<cfif IsDefined('URL.affiliateId') and URL.affiliateId neq "">
    //
</cfif>

Atlantes

As Leigh says: no #'s are requires, plus if you know the scope and variable name you should always use structkeyexists() as shown by scrittler – Hideandseek

yeah I know that #s are required, it's just one of those habits. – Atlantes

Good point about structKeyExists(). Either works, but it is a bit more precise. – Postmeridian

I think they have a CF support group for that .. ;) – Postmeridian

Answer 5

I will just sum up the answers and offer my version of it:

<cfparam name="URL.affiliateId" type="string" default="" />

<cfif len(trim(URL.affiliateId))>
     ...do something with the affiliate...
</cfif>

You do not need structKeyExists or isDefined and it would be better to avoid them. Also you do not need the 'greater than zero' part after the 'len()'.

Gribble

No there are perfectly valid use cases for all of the above. Personal preference, on the other hand, is a different matter. – Postmeridian

Yes, they are valid but not needed. – Jennelljenner

While there are similarities in behavior, there are also differences. So a blanket statement that they are never needed is inaccurate. They do not all provide identical functionality. – Postmeridian