我找不到为什么当我的应用程序退出并重新启动时核心数据 NSManagedObjectContext 没有得到保存。每次我退出应用程序并重新启动时,数据库都是空的
AppDelegate
- (void)applicationWillTerminate:(UIApplication *)application
{
[[ShowScreenManager sharedInstance] reset];
// Saves changes in the application's managed object context before the application terminates.
[self saveContext];
[self.tracker set:kGAISessionControl value:@"end"];
- (void)saveContext
{
NSError *error = nil;
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
if ([managedObjectContext hasChanges] && ![managedObjectContext 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();
}
}
}
保存到核心数据
// get manageObjectContext
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"EntityName"
inManagedObjectContext:context];
[fetchRequest setEntity:entity];
NSError *error;
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
fetchRequest = nil;
if(fetchedObjects.count == 0){
// insert
anItem = [NSEntityDescription
insertNewObjectForEntityForName:@"SomeName"
inManagedObjectContext:context];
}
else{
// update
anItem = [fetchedObjects objectAtIndex:0];
}
aSequnce.all = strSequnce;
// save context
if (![context save:&error]) {
NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
}
}
最佳答案
applicationWillTerminate:
在 iOS 4 之后的版本中基本上从未使用过(当后台运行出现时)。你不应该依赖它做任何事。
您通常应该在更新后保存上下文,而不是等待应用终止。
您可以将您的逻辑移动到 applicationDidEnterBackground:
,但如果您的应用程序崩溃或从 Xcode 终止,它仍然不会被调用。
关于ios - 当 App 退出并重新启动时,NSManagedObjectContext 不会保存,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/34717022/