[AppDelegate managedObjectContext]（发送到实例的无法识别的选择器）

莫问天涯路几重，轻衫侧帽且从容。这篇文章主要讲述[AppDelegate managedObjectContext]：发送到实例的无法识别的选择器相关的知识，希望能为你提供帮助。
我正在按照教程学习核心数据存储和检索。下面是我的表视图代码。

#import "DeviceViewController.h" #import < CoreData/CoreData.h> @interface DeviceViewController () @property(strong) NSMutableArray *devices; @end@implementation DeviceViewController- (NSManagedObjectContext *)managedObjectContext { NSManagedObjectContext *context = nil; id delegate = [[UIApplication sharedApplication] delegate]; if ([delegate performSelector:@selector(managedObjectContext)]) { context = [delegate managedObjectContext]; } return context; } - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; //Fetch the devices from persistent data store NSManagedObjectContext *managedObjectContext = [self managedObjectContext]; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Device"]; self.devices = [[managedObjectContext executeFetchRequest:fetchRequest error:nil] mutableCopy]; [self.tableView reloadData]; }- (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. }#pragma mark - Table view data source-(NSInteger)numberOfSectionsIntableView: (UITableView *)tableView{ return 1; }-(NSInteger)tableView:(UITableView *) tableView numberOfRowsInSection:(NSInteger) section{ return self.devices.count; }-(UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtindexPath:(NSIndexPath *)indexPath{ static NSString *cellIndentifier = @"cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIndentifier forIndexPath:indexPath]; //Configure the cell NSManagedObject *device = [self.devices objectAtIndex:indexPath.row]; [cell.textLabel setText:[NSString stringWithFormat:@" %@ %@ ",[device valueForKey:@"name"],[device valueForKey:@"version"]]]; [cell.detailTextLabel setText:[device valueForKey:@"company"]]; return cell; }

我在创建项目时检查了核心数据的复选框，但是我收到以下错误。

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[AppDelegate managedObjectContext]: unrecognized selector sent to instance 0x60800003c200' *** First throw call stack: ( 0CoreFoundation0x0000000107ab8d4b __exceptionPreprocess + 171 1libobjc.A.dylib0x00000001070f921e objc_exception_throw + 48 2CoreFoundation0x0000000107b28f04 -[NSObject(NSObject) doesNotRecognizeSelector:] + 132 3CoreFoundation0x0000000107a3e005 ___forwarding___ + 1013 4CoreFoundation0x0000000107a3db88 _CF_forwarding_prep_0 + 120 5MyStore0x0000000106b1ff80 -[DeviceViewController managedObjectContext] + 128 6MyStore0x0000000106b20058 -[DeviceViewController viewDidAppear:] + 88 7UIKit0x0000000108084a6c -[UIViewController _setViewAppearState:isAnimating:] + 945 8UIKit0x00000001080b98d7 -[UINavigationController viewDidAppear:] + 207 9UIKit0x0000000108084a6c -[UIViewController _setViewAppearState:isAnimating:] + 945 10UIKit0x00000001080877da __64-[UIViewController viewDidMoveToWindow:shouldAppearOrDisappear:]_block_invoke + 42 11UIKit0x0000000108085ac4 -[UIViewController _executeAfterAppearanceBlock] + 86 12UIKit0x0000000107ee977c _runAfterCACommitDeferredBlocks + 653 13UIKit0x0000000107ed6273 _cleanUpAfterCAFlushAndRunDeferredBlocks + 566 14UIKit0x0000000107ef9757 __84-[UIApplication _handleApplicationActivationWithScene:transitionContext:completion:]_block_invoke_2 + 194 15CoreFoundation0x0000000107a5d6ac __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12 16CoreFoundation0x0000000107a426f4 __CFRunLoopDoBlocks + 356 17CoreFoundation0x0000000107a41e65 __CFRunLoopRun + 901 18CoreFoundation0x0000000107a41884 CFRunLoopRunSpecific + 420 19GraphicsServices0x000000010b952a6f GSEventRunModal + 161 20UIKit0x0000000107edcc68 UIApplicationMain + 159 21MyStore0x0000000106b2132f main + 111 22libdyld.dylib0x000000010a9ae68d start + 1 23???0x0000000000000001 0x0 + 1 ) libc++abi.dylib: terminating with uncaught exception of type NSException

我不熟悉在目标c中使用核心数据。我已经搜索了堆栈和互联网，但无法找到解决方案。
编辑：我的AppDelegate.m如下

#import "AppDelegate.h" #import < CoreData/CoreData.h> @interface AppDelegate ()@end@implementation AppDelegate- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { return YES; } #pragma mark - Core Data stack@synthesize persistentContainer = _persistentContainer; - (NSPersistentContainer *)persistentContainer { // The persistent container for the application. This implementation creates and returns a container, having loaded the store for the application to it. @synchronized (self) { if (_persistentContainer == nil) { _persistentContainer = [[NSPersistentContainer alloc] initWithName:@"MyStore"]; [_persistentContainer loadPersistentStoresWithCompletionHandler:^(NSPersistentStoreDescription *storeDescription, NSError *error) { if (error != nil) { NSLog(@"Unresolved error %@, %@", error, error.userInfo); abort(); } }]; } }return _persistentContainer; }#pragma mark - Core Data Saving support- (void)saveContext { NSManagedObjectContext *context = self.persistentContainer.viewContext; NSError *error = nil; if ([context hasChanges] & & ![context save:& error]) { NSLog(@"Unresolved error %@, %@", error, error.userInfo); abort(); } }@end

正如我所说，我正在关注这个教程，并且AppDelegate类没有任何变化。
答案您的代码有两个问题。 1）您正在使用performSelector（执行操作）而不是respondsToSelector（测试是否允许操作）。 2）appDelete有一个方法persistentContainer而不是managedObjectContext。
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