ColdFusion 8 CFloop Array Iteration / XML Bug?

@Ben:

I'm not sure Adobe would consider this a bug or not. Remember that XML trees are not true ColdFusion arrays, but array-like objects.

It seems to me like this should be classified as a bug though, so I'd definitely recommend you file an ER for this.

Dude, how do you find all this wacky stuff?

I didn't actually realize you could do the implicit XPath navigation thing so I'm in two minds as to whether this is a bug (using xmlChildren gets you *all* the child nodes, not just ones named "actor" so the two are not equivalent).

I would guess that if you call getElementsByTagName("actor") or getChildNodes() you will get an array back...?

@Ben,

I would not consider this a bug really but maybe a feature enhancement. CFLoop does not consider xmlActors.actors.actor an array because it is not really an array. You can use the array notation to get at a specific node if there are more then one with the same name and you can use the array functions, but if you do <cfdump var="#xmlActors.actors.actor#"> right after your CFXML tag it will only dump out the first node so cfdump is not considering it an array automatically either.

I would probably do the loop like:

<cfloop
index="xmlActor"
array="#xmlsearch(xmlActors,'/actors/actor')#">

<!--- Output the data. --->
<p>
#xmlActor.XmlAttributes.name#

<!--- Check to see if date of birth is defined. --->
<cfif (
StructKeyExists( xmlActor.XmlAttributes, "dob" ) AND
Len( xmlActor.XmlAttributes.dob )
)>

(DOB: #xmlActor.XmlAttributes.dob#)

</cfif>
</p>

</cfloop>

What I think might be cool though, is if Adobe adds xmldoc and xpath attributes so you could loop through it like:

<cfloop
index="xmlActor"
XMLDoc="#xmlActors#"
XPath="/actors/actor">

<!--- Output the data. --->
<p>
#xmlActor.XmlAttributes.name#

<!--- Check to see if date of birth is defined. --->
<cfif (
StructKeyExists( xmlActor.XmlAttributes, "dob" ) AND
Len( xmlActor.XmlAttributes.dob )
)>

(DOB: #xmlActor.XmlAttributes.dob#)

</cfif>
</p>

</cfloop>

@Ben,

LOL! I don't know about brilliant... I'm sure you would have figured that out eventually with all the work your doing with XML. I'm all about cutting out the middle man as much as possible, mostly because I'm lazy and don't want to type cfset tags when I don't have to =). Now that I'm thinking about it, a lot of my coolest programs stem from me being too lazy to do some tedious task, so I write some code to do it for me, with as little interaction from me as possible.

@Scott,
I understand putting the array in the actual loop, but doesn't that then cause it to be re-evaluated each time slowing the page processing down?

It's sort of the reason (from other things I've read), that they say to set everything outside of the loop declarations

e.g.
instead of:
for (var i=0; i < arrayLen(myArray);i++) {
loop here
}

do something like:
var arrayLength = arrayLen(myArray)
var i = 0;
for ( ; i < arrayLength;i++) {
loop here
}

(I guess this could also just be put in a while loop then, but just wanted to show my reasoning)

@Gareth,

Only the code within the body of the cfloop tag would get re-evaluated with every iteration, so you would definitely want to make sure any evaluations or other processing you need to do to set up variables that will be used within the body which are not going to change from iteration to iteration are all done before you start the loop.

So you would do this:

<cfset myFavoriteColor = "Blue">
Scott's Favorite Color is
<cfloop index="ThisColor" array="#listtoarray('Red,Green,Blue,Yellow,Black')#">
<cfif ThisColor is myFavoriteColor>#ThisColor#</cfif>
</cfloop>

instead of this:

Scott's Favorite Color is
<cfloop index="ThisColor" array="#listtoarray('Red,Green,Blue,Yellow,Black')#">
<cfset myFavoriteColor = "Blue">
<cfif ThisColor is myFavoriteColor>#ThisColor#</cfif>
</cfloop>

but as Ben said, the stuff within the attributes of the cfloop tag are only evalutated once, and the same would be true if you are using the cfscript syntax.

Yeah I just tested it and there is a difference after all:

<cfset arrData = listtoarray('Red,Green,Blue,Yellow,Black')>
<cfdump var="#arrData#">
<cfscript>
for (i = 1 ; i LTE ArrayLen( arrData ) ; i++){

ArrayDeleteAt( arrData, ArrayLen( arrData ) );

}
</cfscript>
<cfdump var="#arrData#">

doesn't throw an error because it does actually evaluate the "i LTE ArrayLen( arrData )" in every iteration. When you use the cfloop syntax though it gives you an out of bounds error.

<cfset arrData = listtoarray('Red,Green,Blue,Yellow,Black')>
<cfloop index="arrayitem" array="#arrData#">
<cfset ArrayDeleteAt(arrData, ArrayLen( arrData ))>
</cfloop>

<cfdump var="#arrData#">

But a for loop in cfscript is not the equivalent of a cfloop over an array. the for loop is just counting, when looping over the array with a cfloop it is actually setting the index variable to the value of the array item, which would be more like this:

<cfset arrData = listtoarray('Red,Green,Blue,Yellow,Black')>

<cfscript>
end = ArrayLen( arrData );
for (i = 1 ; i LTE end ; i++){
arrayitem = arrdata[i];
ArrayDeleteAt( arrData, ArrayLen( arrData ) );

}
</cfscript>

which throws an error just like the cfloop does.

You may have written about it elsewhere, but it looks like this has been changed in CF9. The index now points to the XML node. Very cool!