Fetch Contacts

fetchContacts.swift

    func findContactsOnBackgroundThread ( completionHandler:@escaping (_ contacts:[CNContact]?)->()) {
        
        DispatchQueue.global(qos: .userInitiated).async(execute: { () -> Void in
            
            let keysToFetch = [CNContactFormatter.descriptorForRequiredKeys(for: .fullName),CNContactPhoneNumbersKey,CNContactViewController.descriptorForRequiredKeys()] as! [CNKeyDescriptor] //CNContactIdentifierKey
            let fetchRequest = CNContactFetchRequest( keysToFetch: keysToFetch)
            var contacts = [CNContact]()

            fetchRequest.unifyResults = true
            fetchRequest.sortOrder = .none

            
            do {
                
                try CNContactStore().enumerateContacts(with: fetchRequest) { (contact, stop) -> Void in
                    //do something with contact
                    if contact.phoneNumbers.count > 0 {
                        contacts.insert(contact, at: 0)
                    }
                    
                }
            } catch let e as NSError {
                print(e.localizedDescription)
            }
            
            DispatchQueue.main.async(execute: { () -> Void in
                completionHandler(contacts)
                
            })
        })
    }