Caution: Java String::Split() Does Not Create A ColdFusion Array
This has been covered before, but you can call the Java string methods on ColdFusion string objects. One of those methods is the String::Split() method. In the Java documentation, it says that it splits this string around matches of the given regular expression. The return value is an array of String objects. When dumped out, these arrays look just like ColdFusion arrays, but they are NOT ColdFusion arrays. ColdFusion arrays are actually Vectors.
To demonstrate that, here are two arrays, one built by ColdFusion and one built by Java:
<!--- Set up the words list. --->
<cfset strWords = "I like to move it, move it!" />
<!---
Create the words array using the underlying
Java method, String::Split().
--->
<cfset arrWordsJava = strWords.Split( " {1}" ) />
<!---
Create the words array using the ColdFusion
function ListToArray().
--->
<cfset arrWordsCF = ListToArray( strWords, " " ) />
Dumping out the Java String::Split() array, we see:
Dumping out the ColdFusion ListToArray() array, we see:
They look exactly the same, right??? Maybe, but they are quite different. From what I can see, the Array returned by the Split() method is read only. If you look at the class methods:
... you can see there are no methods about altering it. In fact, if you try to use ArrayResize() on this array, you get the error:
null null
... and if you try to update one of the values (as in arrWordsJava[ 1 ] = "Ben") you get the error:
You have attempted to dereference a scalar variable of type class coldfusion.runtime.Cast$1 as a structure with members.
Seems like this is read only. The Split() method is really awesome, especially since it splits on a Regular Expression, but just BE CAREFUL, the resultant array is pretty much only for reference.
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Reader Comments
I came acrossed this _exact_ issue yesterday. This explains it.
Consider the following code:
<cfset tzObj=createObject("java","java.util.TimeZone")>
<cfset tzs = tzObj.getAvailableIDs()>
<cfdump var="#tzs#">
<!--- uncomment the next line and you'll get the funky error --->
<!--- <cfset arraySort(tzs, "textnocase")> --->
<!--- rebuild the array manually and the arraySort() works....WEIRD! --->
<cfset foo = arrayNew(1)>
<cfloop from="1" to="#arrayLen(tzs)#" index="i">
<cfset arrayAppend(foo, tzs[i])>
</cfloop>
<!--- no error here --->
<cfset arraySort(foo, "textnocase")>
<cfdump var="#foo#">
So why to some of the array functions work? For example, arrayToList(tzs) works. I ultimately used arrayToList() and listSort() to achieve the desired result.
PS. Noob question - how did you dump the class methods?
Todd,
Yeah, what you are saying makes sense. ArrayToList() must actually iterate over the array to get the value (hence it works with the read-only properties of the array). I guess it is not doing any kind of Join or anything like that.
As far as getting the class methods, I use reflection to get the information about the Java object (works also with ColdFusion objects). Take a look at the ColdFusion User Defined Function I wrote for this:
bennadel.com/index.cfm?dax=blog:206.view
It works 95% of the time. I have to add a try/catch in there for special cases, but so far it's been pretty great.
Read Only !!! That explains why <cfparam name=array[i] wont work on an array created with split...Any other solutions?
@Rob,
You inspired me to finally go think it out:
www.bennadel.com/index.cfm?dax=blog:760.view
ack! this totally bit my arse this morning... grrrr
good to see I'm not the only one that has run into it..
Thanks for the post,
I was looking for this piece of code for ages
I know this blog is old, but arent coldfusion arrays just java lists? I dont think coldfusion arrays are really arrays.