How to set due date in jira issue automatically from version field release date?

[Shagufta Gurmukhdas]

I have a custom field which allows selecting versions. From the selected version in the field, the release date should be extracted and that should be set as the due date for an issue created . (say newSubTask ). How to do that?

What I did was:

def versionCF = customFieldManager.getCustomFieldObjectByName("Fix Version(s)")

String valueOfversionType = parentIssue.getCustomFieldValue(versionCF)

Project project = parentIssue.getProjectObject()

Version versionn = versionManager.getVersion(project.getId(), valueOfversionType)

newSubTask.setDueDate(new Timestamp(versionn.releaseDate.time))

But I get the following error:

2016-11-23 10:18:10,909 ERROR [workflow.ScriptWorkflowFunction]: *************************************************************************************
2016-11-23 10:18:10,911 ERROR [workflow.ScriptWorkflowFunction]: Script function failed on issue: TPK-129, actionId: 1, file: <inline script>
java.lang.NullPointerException: Cannot invoke method getReleaseDate() on null object
	at Script1007.run(Script1007.groovy:61)

[Vasiliy Zverev]

Dear @Shagufta Gurmukhdas, Fix versions is not a custom field. It is a build-in field. To get it you should use 

issue.getFixVersions()

it returns a collection of all Fix Versions.

[Shagufta Gurmukhdas]

No, Fix Version/s is the built-in field, but i have created a custom field named Fix Version(s) since I had to make it mandatory in my project and making mandatory the built in field would have made it mandatory for all projects that use it.

So, basically, my field IS a custom field

[Shagufta Gurmukhdas]

@Vasiliy Zverev can you help with that? with doing it through a custom field?

[Vasiliy Zverev]

1. It is possible to make Fix version mandatory into field configuration

2. Namely trouble is that versionn is null. It means that 

   versionManager.getVersion return null

   Here is modified code

   import com.atlassian.jira.component.ComponentAccessor
   import com.atlassian.jira.issue.Issue
   import com.atlassian.jira.issue.fields.CustomField
   import com.atlassian.jira.project.version.Version
   
   Issue parentIssue = null
   
   CustomField versionCF = customFieldManager.getCustomFieldObjectByName("Fix Version(s)")
   
   Version versionn = versionManager.getVersion(
           parentIssue.getParentObject().getProjectId()
           , parentIssue.getCustomFieldValue(versionCF))
   
   if(versionn == null)
       return
   
   newSubTask.setDueDate(new Timestamp(versionn.getReleaseDate().getTime()))

[Shagufta Gurmukhdas]

Sorry, I have written versionn.getReleaseDate().time, not versionn.releaseDate.time . But anyway, both aren't working