Coredata & NSPersistentDocument: Sum of column numbers crash

Question

I have a problem with a @sum binding of a column in my program:

I'm doing a Coredata, NSPersistentDocument based program. I'm doing mostly everything from IB, the creation of the data model, NSArrayController and NSTableView...

I have just 1 entity with 62 attributes (61 NSString and 1 NSNumber). I import a CSV file with 12722 records. Import works well, can save to xml, binary, sqlite... I've double checked that the overall process works perfect. Can save/load. Everything is there.

The problem that I have: I've created a label that I BIND to @sum of the column with the NSNumber property. This is how I did

>     label->Bindings Inspector->Value
>      Bind to: My_Entity_NSArrayController
>       Controller Key: selection
>       Model Key Path: @sum.myNumericAttribute

When I run the program, click on Import, Select ALL the rows, the @sum works well. It's fast, however and here is the first problem: once I save the file (tried all... binary/xml/sqlite) and later load it and try to Select ALL again, the program crash without error.

Tried through "Profile"->Allocations. I noticed:

• I don't have memory leaks
• When loading from disk and then select all: Goes extremelly slow. After 5 minutes didn't yet finished (I stopped it) and I saw +45MB of CFNumber (Live Bytes) and >1.500.00#Overall. So, something is wrong here, as I'm talking about 12722 rows/registers of type Interger32.

The second problem is the same but reproduced from a different angle. Instead of using "selection" I've tried to use "arrangedObjects". In this case the problem appears even while importing from CSV, it goes extremely slow and it finally crash. Trying to open an already created file also crash.

This is how I did label->Bindings Inspector->Value

>    label->Bindings Inspector->Value
>      Bind to: My_Entity_NSArrayController
>       Controller Key: arrangedObjects
>       Model Key Path: @sum.myNumericAttribute

Can you please help me with some light on what to look for or ideas that can help me find where the problem is?.

Thanks a lot.

Luis

---

---- NEW EDIT AFTER MORE RESEARCH ----

I've found a workaround which I DONT' UNDERSTAND, please comments/answers really appreciated.

My program uses Coredata (SQLite), NSPersistentDocument, NSTableView and an NSArrayController. I want to have a working NSTextField bound to a @sum Collection Operation

Problem: As soon as I open an existing document with SQLite DB populated and I try to bind to the arrangedObjects.@sum.t_24_Bookings from the NSWindowController, the program crash.

My initial guess it's related to the Cannot access contents of an object controller after a nib is loaded however I've followed the recommendation of performing a first Fetch like this without success:

- (void) awakeFromNib
{
    :
    BOOL ok = [[self out_CtEn_Transaction] fetchWithRequest:nil merge:NO error:&error];
    :

Continuing with this idea I've found that if I create a "real" complete Fetch + I perform a @sum access from the Document subclass, then it works.

Here is the code with comments I've put in place in order to have the workaround working.

ABDocument interface (a NSPersistentDocument subclass)

@interface ABDocument : NSPersistentDocument {

    BOOL        ivNewDocument;
    NSArray     *ivFetchedTransactions;
    NSNumber    *ivTotalBookings;
}

@property (nonatomic, getter=isNewDocument) BOOL newDocument;
@property (nonatomic, retain) NSArray   *fetchedTransactions;
@property (nonatomic, retain) NSNumber  *totalBookings;

:

ABDocument implementation

#import "ABDocument.h"
#import "ABWindowController.h"

@implementation ABDocument

@synthesize newDocument                 = ivNewDocument;
@synthesize totalBookings               = ivTotalBookings;
@synthesize fetchedTransactions         = ivFetchedTransactions;

:

/** @brief Create one instance of my custom NSWindowController subclass (ABWindowController)
 *
 * In my NSPersistentDocument I do override makeWindowControllers, where I create 
 * one instance of my custom NSWindowController subclass and use addWindowController: 
 * to add it to the document. 
 *
 */
- (void) makeWindowControllers
{
    // Existing Document?
    if ( ![self isNewDocument]) {
        // NSLog(@"%@:%@ OPENING EXISTING DOCUMENT", [self class], NSStringFromSelector(_cmd));

        // Opening existing document (also has an existing DDBB (SQLite)), so
        // make sure I do perform a first complete "fetch + @sum" to void issues
        // with my NIB bind's.
        [self firstFetchPreventsProblems];
    }

    // Now I can create the Window Controller using my "MainWindow.xib".
    ABWindowController *windowController = [[ABWindowController alloc] init];
    [self addWindowController:windowController];
    [windowController release];    
}


/** @brief First complete "fetch + @sum" to void issues with my NIB bind's.
 *
 *  Before I create the Window Controller with "MainWindow.xib" I have to perform a
 *  first Fetch AND also retrieve a @sum of an NSNumber column.
 *
 *  My NIB has an NSTextField BOUND to @arrangedObjects.@sum.<property> through a NSArrayController
 *  If I don't call this method before the NIB is loaded, then the program will crash.
 *
 */
- (void) firstFetchPreventsProblems {

    // Prepare the Fetch
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Transaction"];

    // 1) Perform the Fetch
    NSError *error = nil;
    [self setFetchedTransactions:[[self managedObjectContext ] executeFetchRequest:request error:&error]];
    if ([self fetchedTransactions] == nil)
    {
        NSLog(@"Error while fetching\n%@",
              ([error localizedDescription] != nil) ? [error localizedDescription] : @"Unknown Error");
        exit(1);
    }

    // 2) Execute Collection Operation @sum
    [self setTotalBookings:[[self fetchedTransactions] valueForKeyPath:@"@sum.t_24_Bookings"]];
}

ABWindowController (The controller that loads my NIB)

- (void)windowDidLoad
{

:
        // PROGRAM CRASH HERE 
        // IF [self firstFetchToPreventsProblems]; is NOT CALLED
        // ABDocument's "makeWindowControllers:"
       [[self totalSumField] bind: @"value" toObject: [self out_CtEn_Transaction]
                       withKeyPath:@"arrangedObjects.@sum.t_24_Bookings" options:nil];

}

Please If you can comment really appreciated, I've got a solution but I don't understand why.

Tanks,
Luis

Answer 1

I found the problem myself after several days researching. It was easy (now that I know):

In parallel I was creating a secondary thread and happened that I was accessing the data model from two different threads. As it's been explained in several Q&As here in Stackoverflow, it's very dangerous.

I've applied the commented solutions in several posts of creating a secondary MOC in the secondary thread.

Now my code is thread safe as per coredata related actions, so program is not crashing.

Thanks again to the community.

Luis