在核心数据更改处理期间捕获到异常
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【中文标题】在核心数据更改处理期间捕获到异常【英文标题】：Exception was caught during Core Data change processing 【发布时间】：2015-07-19 16:00:02 【问题描述】：在我的应用程序中，我在AppDelegate 中创建了我的CoreDataStack，并将该实例传递给我的根视图控制器。在视图控制器中，我连接到一个 API，检索和解析一些 JSON，然后保存到 Core Data。但是，对于大约十分之一的发布，我会立即发生崩溃，这发生在我的 CoreDataStack 类中：
func saveContext ()
if let moc = self.managedObjectContext
var error: NSError? = nil
// This if-statement is the line that gets highlighted following the crash.
if moc.hasChanges && !moc.save(&error)
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
我得到的日志是：
CoreData: error: Serious application error.
Exception was caught during Core Data change processing. This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.
-[__NSCFSet addObject:]: attempt to insert nil with userInfo (null)
2015-07-19 11:33:06.115 AppName[210:3907] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFSet addObject:]: attempt to insert nil'
在我的视图控制器中，我进入主线程以保存到核心数据。崩溃后，在 Debug Navigator 中浏览堆栈时，self.coreDataStack!.saveContext() 会突出显示。我假设我试图在不同的线程上创建和访问managedObjectContext，但似乎并非如此，因为当我调用println(NSThread.currentThread() 时，我得到的线程号和名称与打印时相同来自AppDelegate，我在这里创建了CoreDataStack 实例。
func updateStockInformation(#completion: ((finished: Bool) -> Void)?)
UIApplication.sharedApplication().networkActivityIndicatorVisible = true
if stocks.count > 0
var numberOfStocksUpdated = 0
for stock in stocks
yql.query(stock.symbol, completion: (results) -> Void in
if results != nil
if let query = results!["query"] as? NSDictionary, results = query["results"] as? NSDictionary, quote = results["quote"] as? NSDictionary, lastTradePrice = quote["LastTradePriceOnly"] as? NSString
if let change = quote["Change"] as? NSString
var changeValue = NSDecimalNumber()
if (change as String).hasPrefix("-")
let unsignedNegativeString = change.stringByReplacingOccurrencesOfString("-", withString: "")
let unsignedNegativeNumber = NSDecimalNumber(string: unsignedNegativeString)
let signedNegativeNumber = unsignedNegativeNumber.negative()
changeValue = signedNegativeNumber
else
let unsignedPositiveString = change.stringByReplacingOccurrencesOfString("+", withString: "")
let unsignedPositiveNumber = NSDecimalNumber(string: unsignedPositiveString)
changeValue = unsignedPositiveNumber
if self.market.status == .Open
stock.change = changeValue
var priceValue = NSDecimalNumber()
// Change the 'lastTradePrice' value from an NSString into an NSDecimalNumber
priceValue = NSDecimalNumber(string: lastTradePrice as String)
stock.lastTradePrice = priceValue
stock.profitFromStocksInCompany = self.updateProfitForStock(stock)
numberOfStocksUpdated += 1
if numberOfStocksUpdated == self.stocks.count
dispatch_async(dispatch_get_main_queue(), () -> Void in
println("MainViewController - updateStockInformation: \(NSThread.currentThread())")
println()
self.coreDataStack!.saveContext()
self.updateTotalProfitLabel()
self.reloadPageViewController()
UIApplication.sharedApplication().networkActivityIndicatorVisible = false
self.stockInformationUpdatedDelegate?.stockInformationDidUpdate(self.market.getStatusOfMarket())
completion?(finished: true)
)
)
关于我做错了什么导致偶尔崩溃的任何想法？
【问题讨论】：
【参考方案1】：当我打印出 JSON 数据时，我注意到所有返回的东西都是混乱的，这意味着在接收和解析前一个网络请求的数据之前，for 循环正在快速发送网络请求。所以我决定重组我的代码并使用递归。下面是新改组的代码，它使用递归来更新一只股票的信息，只有在前一只股票的信息被接收、解析和更新后：
func updateStockInformation(#completion: ((finished: Bool) -> Void)?)
updateStock(0, completion: nil)
if stocksUpdatingAppBecameActive
stocksUpdatingAppBecameActive = false
func updateStock(stockIndex: Int, completion: ((finished: Bool) -> Void)?)
var stockIndex = stockIndex
UIApplication.sharedApplication().networkActivityIndicatorVisible = true
if stocks.count > 0
let stock = stocks[stockIndex]
yql.query(stock.symbol, completion: (results) -> Void in
if results != nil
if let query = results!["query"] as? NSDictionary, results = query["results"] as? NSDictionary, quote = results["quote"] as? NSDictionary, lastTradePrice = quote["LastTradePriceOnly"] as? NSString
if let change = quote["Change"] as? NSString
var changeValue = NSDecimalNumber()
// Change the 'change' value from an NSString into an NSDecimalNumber
if (change as String).hasPrefix("-")
let unsignedNegativeString = change.stringByReplacingOccurrencesOfString("-", withString: "")
let unsignedNegativeNumber = NSDecimalNumber(string: unsignedNegativeString)
let signedNegativeNumber = unsignedNegativeNumber.negative()
changeValue = signedNegativeNumber
else
let unsignedPositiveString = change.stringByReplacingOccurrencesOfString("+", withString: "")
let unsignedPositiveNumber = NSDecimalNumber(string: unsignedPositiveString)
changeValue = unsignedPositiveNumber
if self.market.status == .Open
stock.change = changeValue
var priceValue = NSDecimalNumber()
priceValue = NSDecimalNumber(string: lastTradePrice as String)
stock.lastTradePrice = priceValue
stock.profitFromStocksInCompany = self.updateProfitForStock(stock)
self.numberOfStocksUpdated += 1
if self.numberOfStocksUpdated == self.stocks.count
dispatch_async(dispatch_get_main_queue(), () -> Void in
self.coreDataStack!.saveContext()
self.updateTotalProfitLabel()
self.reloadPageViewController()
UIApplication.sharedApplication().networkActivityIndicatorVisible = false
self.stockInformationUpdatedDelegate?.stockInformationDidUpdate(self.market.getStatusOfMarket())
self.numberOfStocksUpdated = 0
completion?(finished: true)
)
else
self.updateStock(stockIndex + 1, completion: nil)
)
【讨论】：
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