import com.atlassian.jira.component.ComponentAccessor
import com.atlassian.jira.issue.IssueFieldConstants
import com.atlassian.jira.issue.fields.FieldManager
import com.atlassian.jira.issue.Issue
// Parent Task Summary
def parentTaskSummary = issue.getParentObject().getSummary()
// getting the list of sub task
Collection<Issue> subTasksList = issue.getSubTaskObjects()
// iterating on the list of sub tasks
for(subTask in subTasksList){
def value = subTask.getCustomFieldValue(ComponentAccessor.getCustomFieldManager().getCustomFieldObjectByName("Component/s"))
}