核心数据 executeFetchRequest 因 exc_bad_access 而失败

Posted 2023-03-04

【中文标题】核心数据 executeFetchRequest 因 exc_bad_access 而失败

【英文标题】：Core data executeFetchRequest fail with exc_bad_access

【发布时间】：2013-09-30 07:33:42

【问题描述】：

据我了解，这是一个内存问题，特别是因为我使用不同的计时器从多个地方多次调用该方法。

下面抛出异常的代码：

- (NSMutableArray*)getAllTraps

    @synchronized(self)
    
        self.fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Trap"];
        NSError *error = nil;
        NSArray *results = [self.managedObjectContext executeFetchRequest:self.fetchRequest error:&error];

        if (!results)
        
            NSLog(@"Error fetching traps: %@", error.localizedDescription);
            NSLog(@"Reason: %@", error.localizedFailureReason);
            NSLog(@"Suggestion: %@", error.localizedRecoverySuggestion);
            abort();
        


        if (error != nil)
        
            // Handle error
            NSLog(@"Error getting all traps");
        
        else
        
            // Handle success
            NSLog(@"Success getting all traps");
        


        NSMutableArray *arrayOfAllTraps = [[NSMutableArray alloc] init];
        for (int i = 0; i < results.count; i++)
        
            Trap *singleTrap = results[i];
            NSMutableDictionary *singleDict = [[NSMutableDictionary alloc] init];

            if (singleTrap.trapID.integerValue > 0)
            
                singleDict[ID] = singleTrap.trapID;
                singleDict[ALARMDISTANCE] = singleTrap.alarmDistance;
                singleDict[ISACTIVE] = singleTrap.isActive;
                singleDict[LAT] = singleTrap.lat;
                singleDict[LON] = singleTrap.lon;
                singleDict[POLYGONS] = singleTrap.polys;


                // NSLog(@"Trap ID: %@, Trap Description: %@", singleTrap.trapID, singleTrap.trapDescription);
                singleDict[DESCRIPTION] = singleTrap.trapDescription;


                singleDict[ROADNUMBER] = singleTrap.roadNumber;
                singleDict[TYPE] = singleTrap.type;
                singleDict[DEGREES] = singleTrap.degrees;
                singleDict[DIRECTION] = singleTrap.direction;


                if (singleTrap.poly0 == nil)
                
                    singleDict[POLYGON_A] = @"";
                
                else
                
                    singleDict[POLYGON_A] = singleTrap.poly0;
                

                // Make sure not to set NULL value #1
                if (singleTrap.poly1 == nil)
                
                    singleDict[POLYGON_B] = @"";
                
                else
                
                    singleDict[POLYGON_B] = singleTrap.poly1;
                

                if (singleTrap.poly2 == nil)
                
                    singleDict[POLYGON_C] = @"";
                
                else
                
                    singleDict[POLYGON_C] = singleTrap.poly2;
                


                // Make sure not to set NULL value #2
                if (singleTrap.polygonAzimut1 == nil)
                
                    singleDict[POLYGON_A_AZIMUTH] = @"";
                
                else
                
                    singleDict[POLYGON_A_AZIMUTH] = singleTrap.polygonAzimut1;
                

                if (singleTrap.polygonAzimut2 == nil)
                
                    singleDict[POLYGON_B_AZIMUTH] = @"";
                
                else
                
                    singleDict[POLYGON_B_AZIMUTH] = singleTrap.polygonAzimut2;
                

                if (singleTrap.polygonAzimut3 == nil)
                
                    singleDict[POLYGON_C_AZIMUTH] = @"";
                
                else
                
                    singleDict[POLYGON_C_AZIMUTH] = singleTrap.polygonAzimut3;
                

                [arrayOfAllTraps addObject:singleDict];
            
        

        return arrayOfAllTraps;
    

失败紧随其后：

NSArray *results = [self.managedObjectContext executeFetchRequest:self.fetchRequest error:&error];

甚至不要进入“如果”。

【问题讨论】：

这可能会有所帮助：***.com/questions/6660851/…

我看到了，这是很老的帖子，因为代码不是 ARC，而我的代码是 arc。

向我们展示 managedObjectContext 初始化代码。你使用什么类型的并发类型？

#define appDelegate ((AppDelegate*)[UIApplication sharedApplication].delegate) self.managedObjectContext = appDelegate.managedObjectContext;

【参考方案1】：

试试这个，

NSFetchRequest *fetch = [[NSFetchRequest alloc] init];
NSEntityDescription *entityDescription = [NSEntityDescription

                                                  entityForName:@"Trap"  inManagedObjectContext:self.managedObjectContext];

[fetch setEntity:entityDescription];

 NSError * error = nil;
 NSArray *results = [self.managedObjectContext executeFetchRequest:fetch error:&error];

【讨论】：

嗨。我正在创建我的 fetch 对象，如下所示： NSFetchRequest *request = [NSFetchRequest new];并像这样设置实体：[request setEntity:entity];我的代码在使用 EXC_BAD_ACCESS 执行获取请求时崩溃。知道为什么吗？