iPhone Core Data不刷新表

发布于 2024-08-20 03:16:10 字数 1145 浏览 5 评论 0原文

我正在尝试使用核心数据编写一个应用程序，并且我已经能够成功读取和写入核心数据数据库。但是，如果我在一个视图控制器中写入数据库，则在关闭应用程序然后再次重新打开之前，其他视图控制器将看不到更改。这真是令人沮丧。我不完全确定如何使刷新 - (void)refreshObject:(NSManagedObject *)object mergeChanges:(BOOL)flag 方法起作用。如何获取对我的托管对象的引用？

无论如何，这是我用来读回数据的代码。这是在 viewDidLoad 方法中。

NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Website" inManagedObjectContext:managedObjectContext];
[request setEntity:entity];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"siteName" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
[sortDescriptor release];
[sortDescriptors release];

NSError *error = nil;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if(mutableFetchResults == nil) {
    //Handle the error
}

[self setNewsTitlesArray:mutableFetchResults];
[mutableFetchResults release];
[request release];

[newsSourcesTableView reloadData];

提前感谢您的帮助！

原文

I'm trying to write an application with Core Data, and I have been able to successfully read and write to the core data database. However, if I write to the database in one view controller, my other view controllers will not see the change until the app is closed then reopened again. This is really frustrating. I'm not entirely sure how to get the refresh - (void)refreshObject:(NSManagedObject *)object mergeChanges:(BOOL)flag method to work. How do I get a reference to my managed object?

Anyways, here's the code I'm using to read the data back. This is in the viewDidLoad method.

NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Website" inManagedObjectContext:managedObjectContext];
[request setEntity:entity];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"siteName" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
[sortDescriptor release];
[sortDescriptors release];

NSError *error = nil;
NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
if(mutableFetchResults == nil) {
    //Handle the error
}

[self setNewsTitlesArray:mutableFetchResults];
[mutableFetchResults release];
[request release];

[newsSourcesTableView reloadData];

Thanks for help in advance!

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ヤ经典坏疍 2024-08-27 03:16:10

我不完全确定您打算做什么，据我所知，您正在一个视图控制器中更改托管对象上下文，并且您希望结果在其他视图控制器中可见，这是正确的吗？无论如何，解决方案是监听 NSManagedObjectContextDidSaveNotification （保存上下文时发送）并将您希望受到更改影响的视图控制器注册为观察者：

NSNotificationCenter *dnc = [NSNotificationCenter defaultCenter];
[dnc addObserver:myController selector:@selector(updateTable:) name:NSManagedObjectContextDidSaveNotification object:controller.context];

myController 控制器中的 updateTable 选择器可能看起来像这样这个：

- (void)updateTable:(NSNotification *)saveNotification
{
if (fetchedResultsController == nil)
{
    NSError *error;
    if (![[self fetchedResultsController] performFetch:&error]) {
    //Update to handle the error appropriately.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        exit(-1);  // Fail
    }       
}
else
{
    NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
    // Merging changes causes the fetched results controller to update its results
    [context mergeChangesFromContextDidSaveNotification:saveNotification];  
    [self.tableView reloadData];
}

希望有帮助。

-奥斯卡

I am not entirely sure what do you intend to do from what I understand you are changing your managed object context in one view controller and you want the result to be visible in other view controllers is this correct?. Anyway a solution for this is to listen for the NSManagedObjectContextDidSaveNotification (which is send when the context is saved) and register as a observer the view controller you want to be afected by the changes:

NSNotificationCenter *dnc = [NSNotificationCenter defaultCenter];
[dnc addObserver:myController selector:@selector(updateTable:) name:NSManagedObjectContextDidSaveNotification object:controller.context];

The updateTable in the myController Controller the selector could look something like this:

- (void)updateTable:(NSNotification *)saveNotification
{
if (fetchedResultsController == nil)
{
    NSError *error;
    if (![[self fetchedResultsController] performFetch:&error]) {
    //Update to handle the error appropriately.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        exit(-1);  // Fail
    }       
}
else
{
    NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
    // Merging changes causes the fetched results controller to update its results
    [context mergeChangesFromContextDidSaveNotification:saveNotification];  
    [self.tableView reloadData];
}

Hope that helps.

-Oscar

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