RESplit() - Splitting Strings With Regular Expressions In ColdFusion

ColdFusion 8 added the ability for the listToArray() function to include empty fields (rather than just skipping over them). Then, ColdFusion 9 added the ability for the listToArray() function to use multi-character delimiters (rather than using each character as a separate delimiter). This is some great functionality; however, I have a love affair with Regular Expressions and I thought it would be nice to have a splitting function that used patterns rather than static delimiters.

As of ColdFusion 8, we have the reMatch() function. This allows us to extract values that match a given pattern. What I've coded here is reSplit(). This allows us to extract values that exist between matches of a given pattern. In essence, reSplit() lets you view a string as a list in which the value delimiters are regular expression pattern matches.

reSplit( regexPattern, string ) :: Array

The reSplit() functionality builds on top of Java's String::split() method. However, rather than using this as an "undocumented" feature, I am using JavaCast() to ensure that I'm dealing with a valid Java string before any splitting is applied.

As you can see, our value argument is passing through JavaCast() before the .split() method is invoked. This split() method takes a regular expression and returns a typed String array. This typed string array then needs to be converted to a valid ColdFusion array.

When we run the above code, we get the following CFDump output:

As you can see, our list was split on the regular expression pattern, ",". This not only split the list, but it maintained the empty values between adjacent delimiters.

NOTE: Because our pattern, in this case, was nothing more than a comma, the same outcome could have been handled with listToArray() and the optional third argument, "includeEmptyFields."

This kind of pattern-based splitting could be great for parsing simple CSV data (ie. data that doesn't have any embedded special characters). Because CSV row delimiters might use the new line, the carriage return, or a combination of the two depending on the originating operating system, we can't really use the listToArray() function. Even with ColdFusion 9's optional argument, "multiCharacterDelimiter," there'd be no way to handle both empty lines as well as the variations in row delimiter.

With pattern-based splitting, however, delimiter variations become much easier:

As you can see, we are splitting the CSV data based on the row-delimiter pattern:

\r\n?|\n

We are then splitting each resultant row on the field-delimiter pattern:

tab

NOTE: Our "tab" here is the variable containing the tab character literal.

When we run this code, we get the following CFDump output:

reMatch() added some awesome extraction functionality in ColdFusion 8; I think that reSplit() would be the prefect complement to that regular expression based parsing.

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