How to decrement a custom field

[Todd Winton]

I would like to decrement the value in a custom field via post function.  I have found the ability to increment by 1 unit (by addon I believe), but not decrement.  

I have tried this using a groovy script post function but believe this is not correct:

issue.get(“customField_10426”) = issue.get(“customField_10426”) - 1

[Mark McCormack (Adaptavist)]

Converting Jamie's comment to an answer:

it's helpful to use that tag, otherwise you will get answers for groovy... JMWU tacks on some extra methods that aren't in the API.

[JamieA]

it's helpful to use that tag, otherwise you will get answers for groovy... JMWU tacks on some extra methods that aren't in the API.

[Todd Winton]

Yes.

[JamieA]

this is using jira misc workflow utils?