数据不会加载到我的 Table 视图中
Data won't load into my Table View
所以我的笔记应用程序有一个 UITableViewController class，其中一切正常，添加、删除和编辑 table 视图。但现在我正在尝试使用 "Realm" 数据库加载数据。我是 iOS (Swift) 的新手，尤其是 Realm，所以我有点困惑。我把它完美地保存到数据库中，当我单击导航栏中的 "Save" 按钮时它就会显示出来。但是当我重新启动应用程序时，table 视图完全是空的。我已经坚持了一段时间，尝试了到目前为止我所知道的一切，但就是无法让它显示出来。有人可以帮助我，也许可以告诉我我做错了什么，或者根本没有做吗？非常感谢。
这也是我的 class
import UIKit
import Realm
class NoteTableViewController: UITableViewController {
// MARK: Properties
var notes = [Note]() // Initialized with a default value (an empty array of Note objects).
override func viewDidLoad() {
super.viewDidLoad()
// Get Realm Database location
println(RLMRealm.defaultRealm().path)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// Return the number of sections.
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// Return the number of rows in the section.
return notes.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
// Table view cells are reused and should be dequeued using a cell identifier.
let cellIdentifier = "NoteTableViewCell"
let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as! NoteTableViewCell
// Fetches the appropriate note for the data source layout in the notes array
let note = notes[indexPath.row]
// Configure the cell...
cell.titleLabel.text = note.title
cell.bodyLabel.text = note.body
return cell
}
// Override to support conditional editing of the table view.
override func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
// Return NO if you do not want the specified item to be editable.
return true
}
// Override to support editing the table view.
override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
// Delete the row from the data source
notes.removeAtIndex(indexPath.row)
// Get the default Realm (Will do this part later)
/*
let realm = RLMRealm.defaultRealm()
realm.beginWriteTransaction()
realm.deleteObject(notes[Int(indexPath.row)])
realm.commitWriteTransaction()
*/
tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
} else if editingStyle == .Insert {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}
}
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "ShowDetail" { // Clicked on a cell
let noteDetailViewController = segue.destinationViewController as! NoteViewController
// Get the cell that generated this segue.
if let selectedNoteCell = sender as? NoteTableViewCell {
let indexPath = tableView.indexPathForCell(selectedNoteCell)!
let selectedNote = notes[indexPath.row]
noteDetailViewController.note = selectedNote
}
}
else if segue.identifier == "AddItem" { // Clicked add button
println("Adding new note")
}
}
@IBAction func unwindToNoteList(sender: UIStoryboardSegue) {
if let sourceViewController = sender.sourceViewController as? NoteViewController, note = sourceViewController.note {
if let selectedIndexPath = tableView.indexPathForSelectedRow() { // User clicked on a row
// Update an existing note.
notes[selectedIndexPath.row] = note
tableView.reloadRowsAtIndexPaths([selectedIndexPath], withRowAnimation: .None)
}
else {
// Add a new note.
let newIndexPath = NSIndexPath(forRow: notes.count, inSection: 0)
notes.append(note)
// Persist in database
let realm = RLMRealm.defaultRealm()
realm.beginWriteTransaction()
Note.createInRealm(realm, withValue: notes[newIndexPath.row])
realm.commitWriteTransaction()
tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Bottom)
}
}
}
}
而这个是笔记对象class
import UIKit // Automatically imports Foundation
import Realm
class Note: RLMObject {
// MARK: Properties
dynamic var title: String = ""
dynamic var body: String = ""
// MARK: Initialization
init?(title: String, body: String) { // Failable initializer
// Initialize stored properties.
self.title = title
self.body = body
super.init()
// Initialization should fail if there is no title
if title.isEmpty {
return nil
}
}
// Must have for Realm to work
override init() {
super.init()
}
}
又过了 2 天就解决了...这是我更新的 class
如 Swinny89 所说，从所有对象中的新笔记对象开始，而不是初始化 "empty" 笔记数组。
import UIKit
import Realm
class NoteTableViewController: UITableViewController {
// MARK: Properties
var notes = Note.allObjects()
override func viewDidLoad() {
super.viewDidLoad()
// Get Realm Database location
println(RLMRealm.defaultRealm().path)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// Return the number of sections.
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// Return the number of rows in the section.
return Int(notes.count)
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
// Table view cells are reused and should be dequeued using a cell identifier.
let cellIdentifier = "NoteTableViewCell"
let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as! NoteTableViewCell
let object = notes[UInt(indexPath.row)] as! Note
// Configure the cell...
cell.titleLabel.text = object.title
cell.bodyLabel.text = object.body
return cell
}
// Override to support conditional editing of the table view.
override func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
// Return NO if you do not want the specified item to be editable.
return true
}
// Override to support editing the table view.
override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
// Delete from database
let realm = RLMRealm.defaultRealm()
realm.beginWriteTransaction()
realm.deleteObject(notes[UInt(indexPath.row)] as! RLMObject)
realm.commitWriteTransaction()
// Delete row from table view
tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
} else if editingStyle == .Insert {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}
}
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "ShowDetail" { // Clicked on a cell
let noteDetailViewController = segue.destinationViewController as! NoteViewController
// Get the cell that generated this segue.
if let selectedNoteCell = sender as? NoteTableViewCell {
let indexPath = tableView.indexPathForCell(selectedNoteCell)!
let selectedNote = notes[UInt(indexPath.row)] as! Note
noteDetailViewController.note = selectedNote
}
}
else if segue.identifier == "AddItem" { // Clicked add button
println("Adding new note")
}
}
@IBAction func unwindToNoteList(sender: UIStoryboardSegue) {
if let sourceViewController = sender.sourceViewController as? NoteViewController, note = sourceViewController.note {
let uuid = NSUUID().UUIDString // Needed for primary key. see below
var unwindedNote = Note()
if let selectedIndexPath = tableView.indexPathForSelectedRow() { // User clicked on a row
// Updating of the note is done in NoteViewController
tableView.reloadRowsAtIndexPaths([selectedIndexPath], withRowAnimation: .None)
}
else {
// Add a new note.
let newIndexPath = NSIndexPath(forRow: Int(notes.count), inSection: 0)
// Persist in database
let realm = RLMRealm.defaultRealm()
realm.beginWriteTransaction()
unwindedNote.title = note.title
unwindedNote.body = note.body
unwindedNote.id = uuid // This is done for the primary key that Realm needs, unique for each object created.
realm.addObjects([unwindedNote])
realm.commitWriteTransaction()
tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Bottom)
}
}
}
}
这是因为您的 Note 数组被初始化为一个空数组，这就是您用来告诉 tableView 有多少行，即 0。
一旦您的 Note 数组已设置并拥有一些数据，您就可以调用 tableView.reloadData() 以重新加载包含数据的数组。
此外，查看上面的代码，您的 class 是从 UITableViewController 继承的，而不是实现 UITableViewControllerDelegate 和 UITableViewControllerDataSource。一旦您的 class 实现了这些，您需要确保在情节提要中或通过代码将 viewController 设置为 tableViewController 的数据源和委托。
所以我的笔记应用程序有一个 UITableViewController class，其中一切正常，添加、删除和编辑 table 视图。但现在我正在尝试使用 "Realm" 数据库加载数据。我是 iOS (Swift) 的新手，尤其是 Realm，所以我有点困惑。我把它完美地保存到数据库中，当我单击导航栏中的 "Save" 按钮时它就会显示出来。但是当我重新启动应用程序时，table 视图完全是空的。我已经坚持了一段时间，尝试了到目前为止我所知道的一切，但就是无法让它显示出来。有人可以帮助我，也许可以告诉我我做错了什么，或者根本没有做吗？非常感谢。
这也是我的 class
import UIKit
import Realm
class NoteTableViewController: UITableViewController {
// MARK: Properties
var notes = [Note]() // Initialized with a default value (an empty array of Note objects).
override func viewDidLoad() {
super.viewDidLoad()
// Get Realm Database location
println(RLMRealm.defaultRealm().path)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// Return the number of sections.
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// Return the number of rows in the section.
return notes.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
// Table view cells are reused and should be dequeued using a cell identifier.
let cellIdentifier = "NoteTableViewCell"
let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as! NoteTableViewCell
// Fetches the appropriate note for the data source layout in the notes array
let note = notes[indexPath.row]
// Configure the cell...
cell.titleLabel.text = note.title
cell.bodyLabel.text = note.body
return cell
}
// Override to support conditional editing of the table view.
override func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
// Return NO if you do not want the specified item to be editable.
return true
}
// Override to support editing the table view.
override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
// Delete the row from the data source
notes.removeAtIndex(indexPath.row)
// Get the default Realm (Will do this part later)
/*
let realm = RLMRealm.defaultRealm()
realm.beginWriteTransaction()
realm.deleteObject(notes[Int(indexPath.row)])
realm.commitWriteTransaction()
*/
tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
} else if editingStyle == .Insert {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}
}
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "ShowDetail" { // Clicked on a cell
let noteDetailViewController = segue.destinationViewController as! NoteViewController
// Get the cell that generated this segue.
if let selectedNoteCell = sender as? NoteTableViewCell {
let indexPath = tableView.indexPathForCell(selectedNoteCell)!
let selectedNote = notes[indexPath.row]
noteDetailViewController.note = selectedNote
}
}
else if segue.identifier == "AddItem" { // Clicked add button
println("Adding new note")
}
}
@IBAction func unwindToNoteList(sender: UIStoryboardSegue) {
if let sourceViewController = sender.sourceViewController as? NoteViewController, note = sourceViewController.note {
if let selectedIndexPath = tableView.indexPathForSelectedRow() { // User clicked on a row
// Update an existing note.
notes[selectedIndexPath.row] = note
tableView.reloadRowsAtIndexPaths([selectedIndexPath], withRowAnimation: .None)
}
else {
// Add a new note.
let newIndexPath = NSIndexPath(forRow: notes.count, inSection: 0)
notes.append(note)
// Persist in database
let realm = RLMRealm.defaultRealm()
realm.beginWriteTransaction()
Note.createInRealm(realm, withValue: notes[newIndexPath.row])
realm.commitWriteTransaction()
tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Bottom)
}
}
}
}
而这个是笔记对象class
import UIKit // Automatically imports Foundation
import Realm
class Note: RLMObject {
// MARK: Properties
dynamic var title: String = ""
dynamic var body: String = ""
// MARK: Initialization
init?(title: String, body: String) { // Failable initializer
// Initialize stored properties.
self.title = title
self.body = body
super.init()
// Initialization should fail if there is no title
if title.isEmpty {
return nil
}
}
// Must have for Realm to work
override init() {
super.init()
}
}
又过了 2 天就解决了...这是我更新的 class
如 Swinny89 所说，从所有对象中的新笔记对象开始，而不是初始化 "empty" 笔记数组。
import UIKit
import Realm
class NoteTableViewController: UITableViewController {
// MARK: Properties
var notes = Note.allObjects()
override func viewDidLoad() {
super.viewDidLoad()
// Get Realm Database location
println(RLMRealm.defaultRealm().path)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// Return the number of sections.
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// Return the number of rows in the section.
return Int(notes.count)
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
// Table view cells are reused and should be dequeued using a cell identifier.
let cellIdentifier = "NoteTableViewCell"
let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as! NoteTableViewCell
let object = notes[UInt(indexPath.row)] as! Note
// Configure the cell...
cell.titleLabel.text = object.title
cell.bodyLabel.text = object.body
return cell
}
// Override to support conditional editing of the table view.
override func tableView(tableView: UITableView, canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
// Return NO if you do not want the specified item to be editable.
return true
}
// Override to support editing the table view.
override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
// Delete from database
let realm = RLMRealm.defaultRealm()
realm.beginWriteTransaction()
realm.deleteObject(notes[UInt(indexPath.row)] as! RLMObject)
realm.commitWriteTransaction()
// Delete row from table view
tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
} else if editingStyle == .Insert {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}
}
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "ShowDetail" { // Clicked on a cell
let noteDetailViewController = segue.destinationViewController as! NoteViewController
// Get the cell that generated this segue.
if let selectedNoteCell = sender as? NoteTableViewCell {
let indexPath = tableView.indexPathForCell(selectedNoteCell)!
let selectedNote = notes[UInt(indexPath.row)] as! Note
noteDetailViewController.note = selectedNote
}
}
else if segue.identifier == "AddItem" { // Clicked add button
println("Adding new note")
}
}
@IBAction func unwindToNoteList(sender: UIStoryboardSegue) {
if let sourceViewController = sender.sourceViewController as? NoteViewController, note = sourceViewController.note {
let uuid = NSUUID().UUIDString // Needed for primary key. see below
var unwindedNote = Note()
if let selectedIndexPath = tableView.indexPathForSelectedRow() { // User clicked on a row
// Updating of the note is done in NoteViewController
tableView.reloadRowsAtIndexPaths([selectedIndexPath], withRowAnimation: .None)
}
else {
// Add a new note.
let newIndexPath = NSIndexPath(forRow: Int(notes.count), inSection: 0)
// Persist in database
let realm = RLMRealm.defaultRealm()
realm.beginWriteTransaction()
unwindedNote.title = note.title
unwindedNote.body = note.body
unwindedNote.id = uuid // This is done for the primary key that Realm needs, unique for each object created.
realm.addObjects([unwindedNote])
realm.commitWriteTransaction()
tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Bottom)
}
}
}
}
这是因为您的 Note 数组被初始化为一个空数组，这就是您用来告诉 tableView 有多少行，即 0。
一旦您的 Note 数组已设置并拥有一些数据，您就可以调用 tableView.reloadData() 以重新加载包含数据的数组。
此外，查看上面的代码，您的 class 是从 UITableViewController 继承的，而不是实现 UITableViewControllerDelegate 和 UITableViewControllerDataSource。一旦您的 class 实现了这些，您需要确保在情节提要中或通过代码将 viewController 设置为 tableViewController 的数据源和委托。