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Ben Nadel
On User Experience (UX) Design, JavaScript, ColdFusion, Node.js, Life, and Love.

REReplace ColdFusion Custom Tag - Another Regular Expression Experiment

By Ben Nadel on
Tags: ColdFusion

It's no secret - I love regular expressions! They are wicked awesome and make my programming life much easier in many ways. In fact, I love them so much that I've tried to come up with many ways to leverage them in ColdFusion loops. Over the weekend, I had another idea; I wanted to try an experiment with regular expressions, ColdFusion custom tags, and closures. This time, I wanted to try to pass an anonymous function body in the "generated content" of the ColdFusion custom tag, and then use that UDF to perform the regular expression replace on the captured groups.

<!--- Store content to replace. --->
<cfsavecontent variable="strText">

	Have you ever been to It's a wicked cool
	site. If you haven't you might want to check out; it has a list of neat
	ColdFusion-based projects that Ben is working on.



	function( $0, $1, $2 ){
		// Check to see if the first group was found (the HTTP)
		// part of the URL. If not, then we need to add it to
		// the HREF so that the link doesn't stay internal.
		if (Len( $1 )){

			return( "<a href=""#$0#"" target=""_blank"">#$0#</a>" );

		} else {

				"<a href=""http://#$0#"" target=""_blank"">#$0#</a>"



<!--- Output updated content. --->
	#HtmlEditFormat( strText )#

As you can see here, we are passing content text to the ColdFusion custom tag. Then, in the tag body, we are defining the function that will be used to replace the matched patterns. In this case, we are auto-linking URLs and adding "http://" when it was not provided (don't get distracted by the regular expression - that's not really the point). When we run this code, we get the following output:

Have you ever been to <a href="**http://**" target="_blank"></a>? It's a wicked cool site. If you haven't you might want to check out <a href="" target="_blank"></a>; it has a list of neat ColdFusion-based projects that Ben is working on.

Notice that in the first link, "", the A tag that we added includes the "http://" in its HREF attribute. This was done using the logic of the UDF defined in the ColdFusion custom tag body.

The way this works is that the body of the ColdFusion custom tag is actually wrapped in a CFSCRIPT tag, written to a temporary file, and then included into the tag context itself. I believe this is called a Closure (Sean Corfield??). This makes the code available to the inner scope of the custom tag where it is subsequently used to replace the matched patterns in the given text.

<!--- Check to see which tag mode we are running. --->
<cfif (THISTAG.ExecutionMode EQ "Start")>

	<!--- Define attributes. --->
	<cfparam name="ATTRIBUTES.Text" type="string" />
	<cfparam name="ATTRIBUTES.Pattern" type="string" />
	<cfparam name="ATTRIBUTES.ReturnVariable" type="variablename" />


		Create the content for the method. When we do this, we
		have to replace the generic name of the function with
		a name to be used internally to this tag.
	<cfsavecontent variable="strMethod">
			#("<" & "cfscript>")#
					"function $(",
			#("</" & "cfscript>")#

	<!--- Get a temporary file. --->
	<cfset strMethodFile = GetTempFile(
		ExpandPath( "/" ),
		) />

	<!--- Write the method to disk. --->

	<!--- Include the file. --->
	<cfinclude template="/#GetFileFromPath( strMethodFile )#" />

		Now that the file has been include and compiled in the
		context of this tag, delete the temporary method file.

	<!--- Create a Java pattern based on the given expression. --->
	<cfset objPattern = CreateObject( "java", "java.util.regex.Pattern" ).Compile(
		JavaCast( "string", ATTRIBUTES.Pattern )
		) />

	<!--- Get the pattern matcher. --->
	<cfset objMatcher = objPattern.Matcher(
		JavaCast( "string", ATTRIBUTES.Text )
		) />

	<!--- Create a string buffer to hold the updated text. --->
	<cfset objBuffer = CreateObject( "java", "java.lang.StringBuffer" ).Init() />

		Get the argument names for the temp method. Since we
		are passing the arguments by name, we need to match
		them up to the groups.
	<cfset arrParameters = GetMetaData( $ ).Parameters />

	<!--- Loop over the matches. --->
	<cfloop condition="#objMatcher.Find()#">

			Build up the argument collection that will be passed
			to the temp replace method.
		<cfset objArguments = {} />

		<!--- Set the complete string match. --->
		<cfset objArguments[ arrParameters[ 1 ].Name ] = objMatcher.Group() />

		<!--- Add each group to arguments. --->

			<!--- Set the argument. --->
			<cfset objArguments[ arrParameters[ intGroup + 1 ].Name ] = objMatcher.Group( JavaCast( "int", intGroup ) ) />

				Check to see if it was found. If not, then set as
				empty string. We need to do this because there is
				no way to say that the arguments are not required.
			<cfif NOT StructKeyExists( objArguments, arrParameters[ intGroup + 1 ].Name )>

					Group was not matched. Send to ColdFusion temp
					method as the empty string.
				<cfset objArguments[ arrParameters[ intGroup + 1 ].Name ] = "" />



		<!--- Get the new replace content. --->
		<cfset strNewContent = $(
			ArgumentCollection = objArguments
			) />

			Now, append the new content to the buffer. This will
			add not only the replacement content but also the
			rest of the text since the last match. When we do
			this, we have to be sure to escape back-references.
		<cfset objMatcher.AppendReplacement(
			REReplace( strNewContent, "([\$\\])", "\\\1", "all" )
			) />


	<!--- Add the rest of the unmatched content. --->
	<cfset objMatcher.AppendTail( objBuffer ) />

		Store the fully updated content in the return variable
		of the CALLER scope.
	<cfset CALLER[ ATTRIBUTES.ReturnVariable ] = objBuffer.ToString() />

		Reset the generated content. We don't want the body of
		the tag to show the method details.
	<cfset THISTAG.GeneratedContent = "" />


As with many of experiments, I don't know if I would ever use it; but, I think it is provides a nice example of how and why it would be awesome to have inline-method definitions in ColdFusion.

Reader Comments


In the END mode of the custom tag, I replace the "function(" with "function $(" before I write it to file. "$" becomes the name of the replace function that I use in the context of the tag. I suppose I should have come up with a better name for it :)


Just curious if you can help me with this....

I have a user enter the following string: website "content approval" new into a text box and need to break it up so that it is 3 separate words eg:

1) website
2) content approval
3) new

I have tried using the following RegEx - "([^\\"]|\\.)*" but this only gets whats enclosed in the double quotes, how can I also select the other 2 words but excluding what I have already picked out within the double quotes?