如何在Swift中打印出核心数据保存错误

Question

如何在Swift中打印出Core Data Save错误？

据我有这两行：

var error: AutoreleasingUnsafePointer<NSError?> = nil
let success = managedObjectContext.save(error)

Answer 1

 func saveContext () {
    if managedObjectContext.hasChanges {
        do {
            try managedObjectContext.save()
        } catch let nserror as NSError {
            // 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.
            print("Unresolved error \(nserror), \(nserror.userInfo)")
            abort()
        }
    }
}

Answer 2

您必须将指针传递给可选的NSError对象。 例如，如果您创建iOS应用并选中“使用核心数据”复选框，则这是Xcode中的模板代码：

func saveContext () {
    if let moc = self.managedObjectContext {
        var error: NSError? = nil
        if moc.hasChanges && !moc.save(&error) {
            // Replace this implementation with code to handle the error appropriately.
            // ...
            NSLog("Unresolved error \(error), \(error!.userInfo)")
            abort()
        }
    }
}