Different Use-Style Of FOR Loop In ColdFusion CFScrpit Tag

Posted January 16, 2007 at 8:38 AM

Tags: ColdFusion

I was reading through Head First Object-Oriented Analysis and Design last night when I came across a neat little snippet of code that used the FOR loop to create an Iterator object and loop through this. This is something I have done in Javascript, but would have never thought to do in ColdFusion (or even thought that it would parse correctly).

When it comes to Iterator usage, I generally use this kind of While loop:

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  • <!--- Create an array. --->
  • <cfset arrParts = ArrayNew( 1 ) />
  •  
  • <!--- Throw some random data in it to populate. --->
  • <cfset ArrayAppend( arrParts, "Ankle" ) />
  • <cfset ArrayAppend( arrParts, "Calves" ) />
  • <cfset ArrayAppend( arrParts, "Thighs" ) />
  • <cfset ArrayAppend( arrParts, "Butt" ) />
  • <cfset ArrayAppend( arrParts, "Boobs" ) />
  • <cfset ArrayAppend( arrParts, "Face" ) />
  •  
  •  
  • <!--- Create an iterator for the array. --->
  • <cfset objIterator = arrParts.Iterator() />
  •  
  • <!---
  • Keep getting the next object from the iterator until
  • will have reached the end of the array and have no
  • more items.
  • --->
  • <cfloop condition="objIterator.HasNext()">
  •  
  • #objIterator.Next()#<br />
  •  
  • </cfloop>

Notice that we have to create the Iterator object before the loop. The CFLoop tag is a bit more restrictive than it's CFScript counterpart. In CFScript (as I was reminded by the Head First book) you can do something like this:

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  • <cfscript>
  •  
  • // Create an Iterator for the array and loop over it.
  • for (
  • objIterator = arrParts.Iterator() ;
  • objIterator.HasNext() ;
  • ){
  •  
  • WriteOutput( objIterator.Next() & "<br />" );
  •  
  • }
  •  
  • </cfscript>

Notice that the Iterator creation AND usage are both part of the FOR loop. Also notice that while there is a second ";" which is required, there is really no "incrementor" for the loop. That is because the incrementing doesn't take place in the FOR loop logic, but rather, it is done via the calls to Next().

Anyway, this is really minor and not functionally different in any way than a While loop, but I think it looks pretty tight.

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Reader Comments

Dan Vega
Jan 16, 2007 at 9:50 AM // reply »
35 Comments
57 Points

I am reading this book as well and what a great book it is. I would like to share thoughts on the book sometime!


Ben Nadel
Jan 16, 2007 at 2:56 PM // reply »
6,516 Comments
25,763 Points

Dan, most definitely. I am only on page 30, so it might be a while, but so far I am liking the typical "Head First" stylings.


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