Ben Nadel
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Ben Nadel at InVision In Real Life (IRL) 2019 (Phoenix, AZ) with: Rich Armstrong
Ben Nadel at InVision In Real Life (IRL) 2019 (Phoenix, AZ) with: Rich Armstrong@richarmstrong )

Randomly Sorting An Array In ColdFusion

By Ben Nadel on
Tags: ColdFusion

I touched upon this a bit when I was talking about randomly sorting a list in ColdFusion. Actually, one of the solutions to that problem was to create, as an interim object, a randomly sorted array. I figured as an example, I would just break it out here to see how it works.

To start with, as always, let's build an array:

  • <!--- Set the number of records. --->
  • <cfset intRecordCount = 4 />
  • <!--- Create an array. --->
  • <cfset arrGirls = ArrayNew( 1 ) />
  • <!--- Resize the array to be our test number. --->
  • <cfset ArrayResize( arrGirls, intRecordCount ) />
  • <!--- Now, we need to populate the array with data. --->
  • <cfloop index="intI" from="1" to="#intRecordCount#" step="1">
  • <!--- Create a struct for the girl data. --->
  • <cfset arrGirls[ intI ] = StructNew() />
  • <!--- Set the ID to be the index. --->
  • <cfset arrGirls[ intI ].ID = intI />
  • <!--- Now, randomly pick a girl to create. --->
  • <cfswitch expression="#RandRange( 1, 3 )#">
  • <cfcase value="1">
  • <cfset arrGirls[ intI ].Name = "Anna" />
  • <cfset arrGirls[ intI ].Hair = "Dirty Blonde" />
  • </cfcase>
  • <cfcase value="2">
  • <cfset arrGirls[ intI ].Name = "Alex" />
  • <cfset arrGirls[ intI ].Hair = "Blonde" />
  • </cfcase>
  • <cfcase value="3">
  • <cfset arrGirls[ intI ].Name = "Jo" />
  • <cfset arrGirls[ intI ].Hair = "Brunette" />
  • </cfcase>
  • </cfswitch>
  • </cfloop>

We should now have an array that is 4 items long:


CFDump 1 : Randomly Sorting An Array In ColdFusion  

I am keeping short for the demo. Now, we want to randomize the order of it. To do this, we are going to loop over the array N times and swap the item at the current index with the a random item in the array. I am not sure how *random* this is. I am sure that are mathematical proofs for determining how many times you should run across the array, but I am not gonna get into it. For now, this seems to work fine:

  • <!---
  • Loop over the array N times. In this case, I am
  • going to be looping twice.
  • --->
  • <cfloop index="intN" from="1" to="2" step="1">
  • <!--- Loop over the array. --->
  • <cfloop index="intI" from="1" to="#ArrayLen( arrGirls )#" step="1">
  • <!---
  • Swap the current item with a randomly chosen item.
  • We are getting the random index via RandRange().
  • --->
  • <cfset ArraySwap(
  • arrGirls,
  • intI,
  • RandRange( 1, ArrayLen( arrGirls ) )
  • ) />
  • </cfloop>
  • </cfloop>

Our array should now be randomly sorted:


CFDump 2 : Randomly Sorting An Array In ColdFusion  

I am not sure about speed testing because I don't really have anything to compare it to. The time it takes to process should increase linearly with the size of the array.

Tweet This Deep thoughts by @BenNadel - Randomly Sorting An Array In ColdFusion Woot woot — you rock the party that rocks the body!

Reader Comments

I think you'll hate me for this... but there is an easy java way to do this.

(this is off the top of my head, but it should work)

Collections = createObject("java", "java.util.Collections");


There you go, the array is shuffled.

(I didn't test this btw, but I can't see why it wouldn't work)


Firstly, I am NEVER gonna hate learning how to do things an easier, simpler way.

Secondly, I am stuck without network access at the moment and can't test this stuff. But, from the documentation on collections, this seems totally valid. I am starting to like this Collections class.

I will test as soon as my boss gets here and give me back my network access :(

and now we learn that Anna is actually a brunette, not a dirty blonde. :-P Haha, just kidding. Good work, Ben.