How to update issuetype based on a custom field value using Update on Transition app

This article helps update the issuetype based on a custom field value using the Update on Transition app.

Instructions

1. Log into Jira as an Administrator.
2. Go to the desired Project > project's Workflow > respective post function. 
   1. If the post function already exists then proceed to step:# 5.
   2. If there is no post function configured then follow the steps from step# 3.
3. Edit the workflow and go to the transition, where you want to add the Update on Transition post function. 
4. Click Add post function and select Bob Swift's Update Issues post function as shown below:
   
5. The post function will have the following condition and regex value. 
    
   Condition value as %original_customfield_11400% where 11400 is the custom field id. 
   Regex pattern will contain the value, here, for example, UoT.
   
   
   
6. Click Update to save the settings.
   
7. Publish the Workflow.
8. Go to any Jira Issue and provide the custom field value UoT and perform the transition.  After the transition happens, the current issuetype gets updated to Epic as shown below.