Post function on transition - alter copy field value

[Aram Dermenjian]

The scene:
I have a transition from Open -> Closed.
I have 2 issue types 'Fixable' and 'Random'.

The Issue:
I want to create a post function so that on transition from open to closed the 'resolved' field is updated based on the issue type. So that:
'fixable' implies that the resolution should be 'fixed'
'random' implies that the resolution should be 'invalid'

Is there anyway to alter the field you are copying over? Alternatively, I could just 'update' the field, but there doesn't seem to be a way to update the field based on some other field.

Is there a way to do something like this? 

[Peter Bengov]

Hey Aram, the JIRA server has a JIRA Workflow Toolbox plugin allows these functions using a post function called Set a Field as a Function of other Fields. Try looking for a plugin with this kind of capability to JIRA Cloud. 

[Aram Dermenjian]

Hey Peter, Yeah, that's the main issue. We need this through cloud. Although your solution and plenty of other ones (e.g. groovy) exist for non-cloud installations, I'd need a cloud specific one.