Destroying ColdFusion Variables Using JavaCast()

Posted July 31, 2006 at 3:22 PM

Tags: ColdFusion

Not really that interesting, but you can destroy variables by setting them equal to the result of a JavaCast() to "null". I have beeing some testing with null values in ColdFusion lately and I did this for a goof:

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  • <!--- Create the objFoo variable. --->
  • <cfset objFoo = StructNew() />
  • <cfset objFoo.Bar = "Well Played!" />
  •  
  • <!--- Destroy struct via JavaCast(). --->
  • <cfset objFoo = JavaCast( "null", 0 ) />
  •  
  • <!--- Dump out variable. --->
  • <cfdump var="#objFoo#" />

This throws the error:

Variable OBJFOO is undefined.

Now, I am not recommending this, nor should this ever be a replacement for the ColdFusion function StructDelete(). In fact, if you try to use this to destroy a structure element, it doesn't "really" work. Let's rework the code to destroy the structure key, not the structure:

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  • <!--- Create the objFoo variable. --->
  • <cfset objFoo = StructNew() />
  • <cfset objFoo.Bar = "Well Played!" />
  •  
  • <!--- Destroy key via JavaCast(). --->
  • <cfset objFoo.Bar = JavaCast( "null", 0 ) />
  •  
  • <!--- Dump out variable. --->
  • <cfdump var="#objFoo#" />

This time, when you dump out the structure, "Bar" is still a key in the structure:


  
  
  

 
undefined struct element  
 
  
  

However, its value is "[undefined struct element]" and any attempt to reference it directly will throw the error:

Element BAR is undefined in OBJFOO.

Interesting stuff.

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Reader Comments

William
Aug 25, 2006 at 11:15 AM // reply »
1 Comments
1 Points

I was trying to figure out how to do this, and this cleared everything up! Thank you!


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