when epic link on a child ticket is changed it should automatically update the custom field to match

[dileep]

1)epic link in child ticket is changed it should automatically update the custom field to match the new epic 
2) whan an epic link is removed from the child ticket the custom field value is cleard?
custom field = GSIRT project field 

by using script runner listener 

thanks 

dileep

[Craig Nodwell · Accepted solution]

Some great examples in the Scriptrunner Library to get you started.
Scriptrunner Library: update-the-value-of-a-custom-field-using-a-listener 

System Events in Jira

Shout out if you hit a brick wall.

[Craig Nodwell]

Another great Scriptrunner Starting Place For Listeners 

[dileep]

@Craig Nodwell  Thanks for response but I am completely new to scripting can you please  share script related to my requirements.

thanks 
dileep

[dileep]

import com.atlassian.jira.component.ComponentAccessor

import com.atlassian.jira.event.type.EventDispatchOption

import com.atlassian.jira.issue.Issue

import com.atlassian.jira.issue.MutableIssue

def issue = event.issue as MutableIssue

def loggedInUser = ComponentAccessor.jiraAuthenticationContext.loggedInUser

def customFieldManager = ComponentAccessor.customFieldManager

def issueManager = ComponentAccessor.issueManager

def issueLinkManager = ComponentAccessor.issueLinkManager

def GSIRTProject = customFieldManager.getCustomFieldObjectsByName('GSIRT Project').first()

def epicLink = customFieldManager.getCustomFieldObjectsByName('Epic Link').first()

def projectGroupValue = issue.getCustomFieldValue(GSIRTProject)

def subTasks = [] as ArrayList<Issue>

if (issue.issueType.name == 'Epic' && issue) {

    def links = issueLinkManager.getOutwardLinks(issue.id)

    links.each {

        def destinationIssue = it.destinationObject as MutableIssue

        destinationIssue.setCustomFieldValue(GSIRTProject, projectGroupValue)

        issueManager.updateIssue(loggedInUser, destinationIssue, EventDispatchOption.DO_NOT_DISPATCH,false)

        destinationIssue.subTaskObjects.findAll {

            subTasks.addAll(it)

        }

    }

} else if(issue.getCustomFieldValue(epicLink)) {

    def links = issueLinkManager.getInwardLinks(issue.id)

    links.each {

       issue.setCustomFieldValue(GSIRTProject, it.sourceObject.getCustomFieldValue(GSIRTProject) )

       issueManager.updateIssue(loggedInUser, issue, EventDispatchOption.DO_NOT_DISPATCH,false)

    }

} else if(issue.getCustomFieldValue(epicLink)==null) {

    issue.setCustomFieldValue(GSIRTProject, null)

    issueManager.updateIssue(loggedInUser, issue, EventDispatchOption.DO_NOT_DISPATCH,false)

} else if(issue.isSubTask()) {

    subTasks.addAll(issue)

}

subTasks.each {

    def subTask = it as MutableIssue

    subTask.setCustomFieldValue(GSIRTProject, it.parentObject.getCustomFieldValue(GSIRTProject))

    issueManager.updateIssue(loggedInUser, subTask, EventDispatchOption.DO_NOT_DISPATCH,false)

}