ios - 核心数据 : `EXC_BAD_ACCESS` When Accessing Objects in Relationship

Question

我有一对多的映射关系，名称匹配和局。

match <-->> innings

• match 有字段名称、id 等。
• innings 有字段编号。

我能够获得 match 属性。我在 TableListController 的 MatchList 中创建了一个新匹配。我看到表中提供了 Match 和 innings 的数据。现在，我单击在表中创建的行。

但是当我执行 [match matchinnings], 时，我得到一个 NSSet* inningSet。我能够从 inningSet 中得到两个对象 inningA 和 inningB。当我尝试调用 [inningA number] 时，出现错误。

下面是我的 NSFetchResultsController 方法:

- (NSFetchedResultsController *)fetchedResultsController {
    // Set up the fetched results controller if needed.
    //NSLog(@"Inside fetchResultsController ");
    if (fetchedResultsController == nil) {
        // Create the fetch request for the entity.
        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        [fetchRequest setReturnsObjectsAsFaults:NO];
        // Edit the entity name as appropriate.
        NSEntityDescription *entity = [NSEntityDescription entityForName:@"Match" inManagedObjectContext:managedObjectContext];
        [fetchRequest setEntity:entity];
        [fetchRequest setRelationshipKeyPathsForPrefetching:[NSArray arrayWithObject:@"matchinnings"]];
        [fetchRequest setIncludesSubentities:YES];
        [fetchRequest setResultType:NSManagedObjectResultType];
        //[fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@"matchinnings.number", nil]];
        //[fetchRequest valueForKeyPath:@"matchinnings.number"];
        //[fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@"matchinnings", @"number", nil]];
        //[fetchRequest setRelationshipKeyPathsForPrefetching:[NSArray arrayWithObject:@"matchinnings.number"]];
        //[fetchRequest setRelationshipKeyPathsForPrefetching:[NSArray arrayWithObjects:@"matchinnings", @"matchinnings.number", nil]];

        // Edit the sort key as appropriate.
        NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:NO];
        NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

        [fetchRequest setSortDescriptors:sortDescriptors];

        // Edit the section name key path and cache name if appropriate.
        // nil for section name key path means "no sections".
        NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"];
        aFetchedResultsController.delegate = self;
        self.fetchedResultsController = aFetchedResultsController;

        [aFetchedResultsController release];
        [fetchRequest release];
        [sortDescriptor release];
        [sortDescriptors release];
    }

    return fetchedResultsController;
} 

在我的 MatchContextMO 类中，我得到一个 EXC_BAD_ACCESS 错误:

inningsArray = [newSet allObjects];

...在这个方法中:

-(NSArray *)determineInningsOrder {

    NSArray* array =  nil;

    NSSet *newSet = [self.match valueForKey:@"matchinnings"];
    NSLog(@"Size of set %d", [newSet count]);

    NSArray *inningsArray = nil;

    @try {
        inningsArray = [newSet allObjects];
    }
    @catch (NSException *exception) {
        NSLog(@"Exception in matchinnings %@", [exception reason]);
    }

    Innings *inningA = [inningsArray objectAtIndex:0];
    Innings *inningB = [inningsArray objectAtIndex:1];

    if ([inningA isKindOfClass:Innings.class])
        NSLog(@"inningA is of type Innings");

    Innings* temp;

    NSNumber *numberA = [inningA valueForKey:@"number"];
    NSLog(@"numberA %d", [numberA intValue]);

    if ([numberA intValue] == 2) {
        temp = inningA;
        inningA = inningB;
        inningB = temp;
    }

    array = [NSArray arrayWithObjects:inningA, inningB, nil];

    return array;
} 

过去一周我一直在努力解决这个问题。它看起来更像是 CoreData 故障。

非常感谢您的帮助。

我尝试迭代返回的集合。 [a addObject:inningsObject] 行仍然出现“EXC_BAD_ACCESS”错误。 NSLog 的大小设置为 2。

-(NSArray *)determineInningsOrder {

    NSArray* array =  nil;

    if (!self.match) {
        NSLog(@"Match is null");
        return nil;
    }


    NSMutableSet *newSet = [self.match valueForKey:@"matchinnings"];
    NSLog(@"Size of set %d", [newSet count]);

    //NSSet *inningsSet = [self.match matchinnings];
    NSArray *inningsArray = nil;

    NSEnumerator *fastEnumerator = [newSet objectEnumerator];

    id inningsObject;
    NSMutableArray *a = [[NSMutableArray alloc] initWithCapacity:[newSet count]];

    while ((inningsObject = [fastEnumerator nextObject])) {
        [a addObject:inningsObject];
    }

    Innings *inningA = [a objectAtIndex:0];
    Innings *inningB = [a objectAtIndex:1];

    [a release];
    if ([inningA isKindOfClass:Innings.class])
        NSLog(@"inningA is of type Innings");

    NSNumber *numberA = [inningA valueForKey:@"number"];
    NSLog(@"numberA %d", [numberA intValue]);

    if ([numberA intValue] == 2) {
        temp = inningA;
        inningA = inningB;
        inningB = temp;
    }

    array = [NSArray arrayWithObjects:inningA, inningB, nil];

    return array;
}

Answer 1

当然，如果您在 CoreData 中将某些东西建模为 Integer 并提供自定义类来实现它。该属性是一个对象:NSNumber。

例子:

.h:

// attributes
@property (nonatomic, retain) NSNumber *version;

// derived attributes
@property (nonatomic, readonly) NSInteger versionIntegerValue;
@property (nonatomic, readonly) NSString *versionStringValue;

.m:

@dynamic version;

- (NSInteger)versionIntegerValue {
  return [self.version integerValue];
}

- (NSString *)versionStringValue {
  return [NSString stringWithFormat:@"v%d", [self.version integerValue]];
}