数据表属性未出现在表视图控制器中

Question

I am new to iOS programming so hopeful that someone can help me with this...

I am using a Table View Controller to display the contents from a data table created using the data model. I have a View Controller that segues to the Table View Controller , which begins by creating the context:

- (void)viewDidLoad {
[super viewDidLoad];

//create managed document memory block
NSFileManager *fileManager = [NSFileManager defaultManager];
NSURL *documentsDirectory = [[fileManager URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] firstObject];
NSString *documentName = @"MyDatabaseTest";
NSURL *url = [documentsDirectory URLByAppendingPathComponent:documentName];
UIManagedDocument *document = [[UIManagedDocument alloc] initWithFileURL:url];

//check to see if file already exists
BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:[url path]];

//if yes, do something, if not open/save
if (fileExists) {
    [document openWithCompletionHandler:^(BOOL success) {
        if (success) [self documentIsReady:document];
        if (!success) NSLog(@"couldn't open document at %@", url);
    }];
}  else  {
    [document saveToURL:url forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
        if (success) [self documentIsReady:document];
        if (!success) NSLog(@"couldn't open document at %@", url);
    }];
}

}

- (void)documentIsReady:(UIManagedDocument *)document  {

if (document.documentState == UIDocumentStateNormal)  {
    NSManagedObjectContext *context = document.managedObjectContext;
    self.context = context;

}

}

Then add the object in the segue:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([sender isKindOfClass:[UIButton class]])  {
    NSIndexPath *indexPath = sender;
    NSDictionary *currentDictionaryItem = self.projectDictionary;
    NSString *currentName = [currentDictionaryItem valueForKeyPath:@"name"];

    if (indexPath)  {
        if ([segue.identifier isEqualToString:@"TableSegue"])  {
            [segue.destinationViewController setTitle:currentName];
//                NSLog(@"the mutable dictionary includes = %@",currentName);

            [Project newProjectCreation:self.projectDictionary inManagedObjectContext:self.context];

            ProjectsCDTVC *pcdtvc = [[ProjectsCDTVC alloc] init];
            [pcdtvc makeContext:self.context];

        }
    }
  }
}

The object appears to be added to the data table correctly, but when I call the Core Data Table View Controller subclass, ProjectsCDTVC , cellForRowAtIndexPath never gets called. ProjectsCDTVC is designated as the Custom Class for the Table View Controller in the storyboard as well.

-(void)makeContext:(NSManagedObjectContext *)myContext
{

_managedObjectContext = myContext;

//request into Project table
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Project"];


//get all projects when predicate is nil
request.predicate = nil;
request.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES selector:@selector(localizedStandardCompare:)]];
request.fetchLimit = 100;

self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
   NSLog(@"the managed object context is %@",self.managedObjectContext);
} 

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{


UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:@"Project Cell"];

Project *project = [self.fetchedResultsController objectAtIndexPath:indexPath];

cell.textLabel.text = project.name;

return cell;
}

I saw a related post that noted that if the number of sections in the table view is zero that cellForRowAtIndexPath will not get called so I watched the sections variable. Sections initially had a correct value of '1' but, at some point, got reset to '0'. I have been debugging for some time and cannot locate why sections is getting reset so any help would be much appreciated!

Answer 1

You're passing the context to a newly created instance of ProjectsCDTVC that you never use, and will be immediately deallocated. You need to pass it to the segue.destinationViewController.

ProjectsCDTVC *pcdtvc = segue.destinationViewController;
[pcdtvc makeContext:self.context];