我有一张表以下列方式工作。如果选择了行，则会将与所选行对应的金额添加到var total，并添加复选标记。如果取消选择，将减去金额，复选标记将设置为无。
在尝试向/从NSUserDefaults保存/检索数据之前，我的代码工作正常。
错误是：当我选择第一行时，它会减去金额而不是添加金额;选择一行后，如果我点击后退按钮然后返回到同一屏幕，则不会显示复选标记。
在此构造中，当我尝试从NSUserDefaults indexPathForCellSelected检索时，求值为nil，即使我在进行赋值之前检查if indexPathForCellSelected != nil。
致命错误：在解包可选值时意外发现nil
if indexPathForCellSelected != nil { self.tableView.cellForRowAtIndexPath(indexPathForCellSelected!)?.
accessoryType = .Checkmark
}
class NinethViewController: UIViewController, UITableViewDelegate,UITableViewDataSource {
var total = 0
var indexRowRetrieved:Int?
var rowSelected:Int?
var indexRowSelectedKey = "indexRowKey"
var amountKey = "amountKey"
var totalKey = "totalKey"
let indexPathKey = "indexPathForCellSelected"
var indexPathForCellSelected: NSIndexPath?
struct Item {
var name:String // name of the row
var selected:Bool // whether is selected or not
var amount: Int // value of the item
}
var extras = [
Item(name:"Inside Cabinets",selected: false, amount: 5),
Item(name:"Inside Fridge",selected: false, amount: 5),
Item(name:"Inside Oven",selected: false, amount: 5),
Item(name:"Laundry wash & dry",selected: false, amount: 10),
Item(name:"Interior Windows", selected: false, amount: 5)
]
@IBOutlet weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
// loadData from NSUserDefaults
loadData()
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return extras.count
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1
}
// configure the cell
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath)
-> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell")
cell?.textLabel?.text = extras[indexPath.row].name
return cell!
}
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
// if the cell has not been selected before
if !extras[indexPath.row].selected {
// marks the cell as selected
extras[indexPath.row].selected = true
tableView.cellForRowAtIndexPath(indexPath)?.accessoryType = .Checkmark
self.total += extras[indexPath.row].amount
indexPathForCellSelected = indexPath
rowSelected = indexPath.row
print(total)
// save all info in NSUserDefaults
saveData()
} else {
// marks the cell as not selected
extras[indexPath.row].selected = false
tableView.cellForRowAtIndexPath(indexPath)?.accessoryType = .None
self.total -= extras[indexPath.row].amount
print(total)
}
}
func saveData(){
// save indexPathForCellSelected in NSUserDefaults
if indexPathForCellSelected != nil {
let data = NSKeyedArchiver.archivedDataWithRootObject(indexPathForCellSelected!)
NSUserDefaults.standardUserDefaults().setObject(data, forKey: indexPathKey)
// save indexRowSelected
NSUserDefaults.standardUserDefaults().setInteger(rowSelected!, forKey: indexRowSelectedKey)
// save amount for corresponding row in NSUserDefaults
NSUserDefaults.standardUserDefaults().setObject(extras[rowSelected!].amount, forKey: amountKey)
//save total in NSUserDefaults
NSUserDefaults.standardUserDefaults().setObject(total, forKey: totalKey)
}
}
func loadData() {
//retrieve indexPathForCellSelected from NSUserDefaults
if let retrievedIndexPath = NSUserDefaults.standardUserDefaults().dataForKey(indexPathKey) {
if let data1 = NSKeyedUnarchiver.unarchiveObjectWithData(retrievedIndexPath) as? NSIndexPath{
indexPathForCellSelected = data1
}
}
// retrieve the index for row selected to select the state of the row: true or false
if let retrievedIndexRow = NSUserDefaults.standardUserDefaults().integerForKey(indexRowSelectedKey) as? Int {
indexRowRetrieved = retrievedIndexRow
extras[retrievedIndexRow].selected = true
}
// retrieve amount for corresponding row in NSUserDefaults
if let itemAmount = NSUserDefaults.standardUserDefaults().objectForKey(amountKey) as? Int {
extras[indexRowRetrieved!].amount = itemAmount
// assign checkmark to row selected
if indexPathForCellSelected != nil {
self.tableView.cellForRowAtIndexPath(indexPathForCellSelected!)?.accessoryType = .Checkmark
}
}
// retrieve total from NSUserDefaults
if let totalRetrieved = NSUserDefaults.standardUserDefaults().objectForKey(totalKey) as? Int {
total = totalRetrieved
print(total)
}
}
}
答案 0 :(得分：1)
尝试使用表达式在tableView(_:didSelectRowAtIndexPath:)函数中添加复选标记，您还应该能够根据其状态实现加法和减法。所以你可以这样做：
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
if let cell = tableView.cellForRowAtIndexPath(indexPath) {
if cell.accessoryType == .None {
cell.accessoryType = .Checkmark
total += extras[indexPath.row].amount
} else if cell.accessoryType == .Checkmark {
cell.accessoryType = .None
total -= extras[indexPath.row].amount
}
// Call function to save here
}
}
答案 1 :(得分：1)
根据您之前提出的问题，我不知道为什么要为之前选择的单元保存所有NSIndexPath，您需要只保存单元格的索引选中以及转到另一个控制器时的总值。您可以通过以下方式完成此操作：
var frequency = [
Item(name:"Every week",selected: false, amount: 30),
Item(name:"Every 2 weeks",selected: false, amount: 30),
Item(name:"Every 4 weeks",selected: false, amount: 30),
Item(name:"Once",selected: false, amount: 40),
Item(name:"End of tenancy cleaning", selected: false, amount: 44)
]
var indexPathForCellSelected: NSIndexPath?
var total = 0
let indexPathKey = "indexPathForCellSelectedNinethViewControllerKey"
let totalKey = "totalNinethViewControllerKey"
override func viewDidLoad() {
super.viewDidLoad()
loadData()
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)
cell.textLabel?.text = frequency[indexPath.row].name
if let _ = indexPathForCellSelected where indexPath == indexPathForCellSelected {
cell.accessoryType = .Checkmark
}
return cell
}
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
if !frequency[indexPath.row].selected {
// this avoid set initial value for the first time
if let index = indexPathForCellSelected {
// clear the previous cell
frequency[index.row].selected = false
tableView.cellForRowAtIndexPath(index)?.accessoryType = .None
self.total -= frequency[index.row].amount
}
// mark the new one
frequency[indexPath.row].selected = true
tableView.cellForRowAtIndexPath(indexPath)?.accessoryType = .Checkmark
indexPathForCellSelected = indexPath
self.total += frequency[indexPath.row].amount
saveData()
}
}
private func saveData() {
// save the index for the cell selected in NSUserDefaults
NSUserDefaults.standardUserDefaults().setInteger(indexPathForCellSelected!.row, forKey: indexPathKey)
// save total in NSUserDefaults
NSUserDefaults.standardUserDefaults().setInteger(total, forKey: totalKey)
}
private func loadData() {
// get the values from NSUserDefaults if exist
if let indexValue = NSUserDefaults.standardUserDefaults().valueForKey(indexPathKey), totalValue = NSUserDefaults.standardUserDefaults().valueForKey(totalKey) {
indexPathForCellSelected = NSIndexPath(forRow: indexValue as! Int, inSection: 0)
total = totalValue as! Int
}
}
我希望这对你有所帮助。
答案 2 :(得分：0)
这是我的问题的正确答案。如果有人有更好的方法，请在答案部分发布您的版本。
class NinethViewController: UIViewController, UITableViewDelegate,UITableViewDataSource {
var total = 0
var totalKey = "totalNinethViewControllerKey"
let indexPathKey = "indexPathForCellSelectedNinethViewControllerKey"
var indexPathsForCellSelected: NSMutableSet = NSMutableSet()// {NSIndexPath}
struct Item {
var name:String // name of the row
var selected:Bool // whether is selected or not
var amount: Int // value of the item
}
var extras = [
Item(name:"Inside Cabinets",selected: false, amount: 5),
Item(name:"Inside Fridge",selected: false, amount: 5),
Item(name:"Inside Oven",selected: false, amount: 5),
Item(name:"Laundry wash & dry",selected: false, amount: 10),
Item(name:"Interior Windows", selected: false, amount: 5)
]
@IBOutlet weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
// loadData from NSUserDefaults
self.loadData()
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return extras.count
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1
}
// configure the cell
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath)
-> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell")
cell?.textLabel?.text = extras[indexPath.row].name
return cell!
}
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
// if the cell has not been selected before
if !extras[indexPath.row].selected {
// marks the cell as selected once
extras[indexPath.row].selected = true
tableView.cellForRowAtIndexPath(indexPath)?.accessoryType = .Checkmark
self.total += extras[indexPath.row].amount
indexPathsForCellSelected.addObject(indexPath)
print("selecting")
print(total)
} else {
// marks the cell as not selected
extras[indexPath.row].selected = false
tableView.cellForRowAtIndexPath(indexPath)?.accessoryType = .None
self.total -= extras[indexPath.row].amount
indexPathsForCellSelected.removeObject(indexPath)
print(total)
}
// save all info in NSUserDefaults
self.saveData()
}
func saveData() {
// save indexPathsForCellSelected in NSUserDefaults
let data = NSKeyedArchiver.archivedDataWithRootObject(indexPathsForCellSelected)
NSUserDefaults.standardUserDefaults().setObject(data, forKey: indexPathKey)
//save total in NSUserDefaults
NSUserDefaults.standardUserDefaults().setObject(total, forKey: totalKey)
}
func loadData() {
//retrieve indexPathForCellSelected from NSUserDefaults
if let retrievedIndexPath = NSUserDefaults.standardUserDefaults().dataForKey(indexPathKey) {
if let data1 = NSKeyedUnarchiver.unarchiveObjectWithData(retrievedIndexPath) as? NSMutableSet{
indexPathsForCellSelected = data1
}
}
// assign checkmark to row selected
for item in indexPathsForCellSelected {
if let indexPath = item as? NSIndexPath {
extras[indexPath.row].selected = true
self.tableView.cellForRowAtIndexPath(indexPath)?.accessoryType = .Checkmark
/* let tableV = self.tableView
let cell = tableV.cellForRowAtIndexPath(indexPath)
extras[indexPath.row].selected = true
cell?.accessoryType = .Checkmark */
}
}
// retrieve total from NSUserDefaults
if let totalRetrieved = NSUserDefaults.standardUserDefaults().objectForKey(totalKey) as? Int {
total = totalRetrieved
print(total)
}
}
}
答案 3 :(得分：-3)
尝试在设置数据后同步NSUserDefaults。
let defaults = NSUserDefaults.standardUserDefaults()
defaults.setObject("1", forKey: "SomeKey")
defaults.synchronize() // Sync the defaults to update the data