I think this would be the most straightforward way, RegEx in the stringsearcher then the value of anything coming out the not matched port can be set to a default value

You could do something like this in an attributecreator, but returning the matched regex is more complicated, especially if like you say, the regex you will be using is more complicated. This example tests for the presence of the regex, if -1 is returned it means no match and a default value is set, otherwise everything that does NOT match the regex is replaced with nothing (leaving just the matched value)

Thanks for the quick response. I contemplated that solution and may end up using it, but it does have an undesirable aspect that violates the DRY principle of coding. Don't Repeat Yourself. The Code1 attribute has to be created twice, setting up a booby trap for my future self, or future others.

keep the '_first_match' attribute from the StringSearcher. connect all output pipe to attributecreator and create a conditional statement where if(_first_match has value, a,d)

You also could skip the stringsearcher and just use the attributecreator

I flipped the order from to put attribute creator first, filled all values with 'd', then ran the string searcher over overwrote as necessary. That's a bit cleaner and adheres to DRY. I'm still up for any other ideas y'all have.

@townest​ why aren't you using conditional values in the attributecreator? You could eliminate stringsearcher

I'm learning which is why I'm asking. Conditional values sound like a good plan, but I'm stuck on a few details. Primarily, how to return a matched pattern. How do you write:

If regexpattern(a) in 'abc' then return regexpattern(a);

else 'd'?

bid (string) code1 (result)

abc a

xyz d

baw a

Remember my regex is more complex than 'a' so the result has to be the actual matched pattern and not just a constant 'a' as shown in @alexlynch3450​  recommended screen shots above.

Thanks for your help.

okay, to help you set things straight use a tester transformer before production.

1. In the tester transformer, add left attribute, change operator to "CONTAINS REGEX", and navigate to "Open Regex Editor". Test your ~complex` pattern.
2. run data through to verify test clauses worked.
3. disable tester and add attributecreator
   1. pick conditional statement and take regex test clause from tester transformer

The issue is returning the matched pattern is not straightforward in an attributecreator. I've demonstrated one way you can do it but the regex becomes more complicated. If the match is a fixed length it's possible to do it by finding the position of the matched pattern and then using that to get the substring.

The stringsearcher is a much easier way to get the match and it's likely much easier for someone else reading the workspace to understand what is going on.

@townest​  For a DRY solution and only one AttributeCreator, I think you should be able to use a capture group and back-reference \\1 in @repalceRegex()

In the AttributeCreator - use a conditional with Contains Regex to find your pattern. But in the Attribute Value field, use @ReplaceRegEx() with a capture group and the back-reference \\1

I've attached an example workspace.

I never knew you could use capture groups in the AttributeCreator. Matching everything and then returning just the group works, but once you start getting into lookahead and lookbehind regex it gets a bit complicated. I've never understood why there isn't a simple ReturnRegExMatch option?

@ebygomm​ well we both learnt something today! We are planning a @SubstringRegex() function so I have added your thoughts to the change request. . Not sure when it will appear in FME.

I've a similar approach that only make one Regex call:

The conditional for 'Code' simply tests whether 'Code' has a value and if not set 'Code' = "<Default>".

From there I get these results:

@Mark Stoakes​, Thank you. I'll give your solution a whirl when I get a chance. Tyler