我已经使用 Realm 一段时间了，我对它非常满意！但是，我在执行过程中偶然发现了一些问题。
我制作了一个测试场景，试图指出我需要输入的地方。
我有一个带有 Person 对象数据库的领域。这些都呈现在 UITableView 中。我想保持对象的特定顺序，并且用户应该能够重新排序对象。从我读过的内容来看，我必须使用 Realms 'List' 来实现这一点。这再次意味着我有一个名为 Person 的类和一个名为 PersonList 的类。PersonList 只有一个属性： - list。
应用程序的 Realm 中应该只有一个 PersonList 对象，但可能有多个 Person 对象。
我的问题：
在我的领域中只有一个 PersonList 实例的最佳做法是什么？正如您在下面的示例中看到的，我首先检查是否存在，如果不存在，则创建它。
使用领域通知的最佳实践是什么。将它添加到我的领域中一个 PersonList 对象的列表属性是否正确？
假设我想要一个单独的类来处理我的领域中的写事务。正如您在我的示例中看到的那样，所有读/写事务都保存在 UITableViewController 类中——这被认为是混乱的吗？
我下面的示例应该能够使用 Xcode 8、Swift 3 和 Realm 1.1.0 正常运行。
我感谢任何反馈和想法！
问候， 埃里克
import UIKit
import RealmSwift
class PersonList : Object {
var list = List<Person>()
}
class Person : Object {
dynamic var favorite = false
dynamic var username : String?
dynamic var firstName : String?
dynamic var lastName : String?
var fullName : String? {
get {
guard let firstName = firstName, let lastName = lastName else {
return nil
}
return "\(firstName) \(lastName)"
}
}
}
class ViewController: UITableViewController {
var results : List<Person>?
var notificationToken: NotificationToken? = nil
func addPerson() {
let alert = UIAlertController(title: "Add Person", message: "Please fill in the information", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
alert.addAction(UIAlertAction(title: "Add", style: .default, handler: { alertAction in
if let firstNameTextField = alert.textFields?[0], let lastNameTextField = alert.textFields?[1] {
self.savePerson(firstName: firstNameTextField.text, lastName: lastNameTextField.text)
}
}))
alert.addTextField { (textField : UITextField!) -> Void in
textField.placeholder = "First Name"
}
alert.addTextField { (textField : UITextField!) -> Void in
textField.placeholder = "Last Name"
}
self.present(alert, animated: true, completion: nil)
}
func savePerson(firstName: String?, lastName: String?) {
guard let firstName = firstName, !firstName.isEmpty else {
let alert = UIAlertController(title: "Oops!", message: "First name missing!", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
self.present(alert, animated: true, completion: nil)
return
}
guard let lastName = lastName, !lastName.isEmpty else {
let alert = UIAlertController(title: "Oops!", message: "Last name missing!", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
self.present(alert, animated: true, completion: nil)
return
}
let realm = try! Realm()
let newPerson = Person()
newPerson.firstName = firstName
newPerson.lastName = lastName
newPerson.username = "\(Date())"
do {
try realm.write {
results?.append(newPerson)
}
}
catch let error {
print("Error: \(error)")
}
}
func editButtonAction(_ sender: UIBarButtonItem) {
if tableView.isEditing {
tableView.setEditing(false, animated: true)
sender.title = "Edit"
}
else {
tableView.setEditing(true, animated: true)
sender.title = "Done"
}
}
override func viewDidLoad() {
super.viewDidLoad()
let addButton = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(self.addPerson))
let editButton = UIBarButtonItem(title: "Edit", style: UIBarButtonItemStyle.plain, target: self, action: #selector(self.editButtonAction(_:)))
self.navigationItem.rightBarButtonItems = [addButton, editButton]
tableView.allowsSelectionDuringEditing = true
let realm = try! Realm()
//First, make sure a list exists in realm
if realm.objects(PersonList.self).first?.list == nil {
print("No existing list found in realm. Creating one.")
let defaultList = PersonList()
do {
try realm.write {
realm.add(defaultList)
}
}
catch let error { print("Error creating person list: \(error)") }
}
results = realm.objects(PersonList.self).first?.list
// Observe Results Notifications
notificationToken = results?.addNotificationBlock { [weak self] (changes: RealmCollectionChange) in
guard let tableView = self?.tableView else { return }
switch changes {
case .initial:
// Results are now populated and can be accessed without blocking the UI
tableView.reloadData()
break
case .update(_, let deletions, let insertions, let modifications):
// Query results have changed, so apply them to the UITableView
tableView.beginUpdates()
tableView.insertRows(at: insertions.map { IndexPath(row: $0, section: 0) }, with: .automatic)
tableView.deleteRows(at: deletions.map { IndexPath(row: $0, section: 0) }, with: .automatic)
tableView.reloadRows(at: modifications.map { IndexPath(row: $0, section: 0) }, with: .automatic)
tableView.endUpdates()
break
case .error(let error):
// An error occurred while opening the Realm file on the background worker thread
print("Error: \(error)")
break
}
}
}
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return results?.count ?? 0
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let reuseIdentifier = "PersonTestCell"
var cell = tableView.dequeueReusableCell(withIdentifier: reuseIdentifier)
if cell == nil {
cell = UITableViewCell(style: UITableViewCellStyle.subtitle, reuseIdentifier: reuseIdentifier)
}
if let results = self.results {
let person = results[indexPath.row]
cell!.textLabel?.text = person.fullName ?? "Name not found."
cell!.detailTextLabel?.text = person.username ?? "Username not found."
}
return cell!
}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
tableView.deselectRow(at: indexPath, animated: true)
}
// Override to support conditional editing of the table view.
override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
return true
}
// Override to support editing the table view.
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
if let results = self.results {
//Delete Person
let realm = try! Realm()
do {
try realm.write {
results.remove(objectAtIndex: indexPath.row)
}
}
catch let error {
print("Error: \(error)")
}
}
}
}
override func tableView(_ tableView: UITableView, editingStyleForRowAt indexPath: IndexPath) -> UITableViewCellEditingStyle {
return UITableViewCellEditingStyle.delete
}
// Override to support rearranging the table view.
override func tableView(_ tableView: UITableView, moveRowAt fromIndexPath: IndexPath, to toIndexPath: IndexPath) {
let realm = try! Realm()
do {
try realm.write {
results?.move(from: toIndexPath.row, to: fromIndexPath.row)
results?.move(from: fromIndexPath.row, to: toIndexPath.row)
}
}
catch let error {
print("Error: \(error)")
}
}
// Override to support conditional rearranging of the table view.
override func tableView(_ tableView: UITableView, canMoveRowAt indexPath: IndexPath) -> Bool {
// Return false if you do not want the item to be re-orderable.
return true
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
deinit {
notificationToken?.stop()
}
}