CNPurgeGroup.swift

//MIT

import Foundation
import Contacts

if(NSProcessInfo.processInfo().arguments.count != 2) {
    print("Usage: CNPurgeGroup %GROUPNAME%")
}
else {
    let groupName = NSProcessInfo.processInfo().arguments[1]
    
    let store = CNContactStore()
    let groups = try! store.groupsMatchingPredicate(nil)
    for group in groups {
        if(group.name == groupName) {
            let groupIdentifer = group.identifier
            let relevantPredicate = CNContact.predicateForContactsInGroupWithIdentifier(groupIdentifer)
            let contacts = try! store.unifiedContactsMatchingPredicate(relevantPredicate, keysToFetch: [CNContactGivenNameKey])
            
            let saveRequest = CNSaveRequest()
            for contact in contacts {
                saveRequest.deleteContact(contact.mutableCopy() as! CNMutableContact)
            }
            try! store.executeSaveRequest(saveRequest)
        }
    }
    
}

since deleting a contact from a group in the contacts app only removes it from the group, I wrote this short snippet to 'purge' a group