iPhone – NSMutableDictionary causes EXC_BAD_ACCESS

self.ridesDict = [self loadHistoryFromDBExtended]; 

NSLog(@"rides dict %@", self.ridesDict); 
However, I don’t want to call [self loadHistoryFromDBExtended] for each unit being loaded, because the dictionary will not change, so I try to move:
 
 
self.ridesDict = [self loadHistoryFromDBExtended];
to viewDidLoad, now I receive an EXC_BAD_ACCESS error when I use it:

NSLog(@"rides dict %@", self. ridesDict);
In the tableView: cellForRowAtIndexPath: indexPath. From what I can see, it seems that I have some memory retention/release issues, but I can’t seem to figure it out. After calling the loadHistoryFromDBExtended method, I’m in I tried [self.ridesDict retain] in viewDidLoad, but it did not help. I am very new to this, so I appreciate any suggestions on where to go.
Edit: This is the loadHistoryFromDBExtended method:

-(NSMutableDictionary *)loadHistoryFromDBExtended
{ 
 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

 FMDatabase* db = [FMDatabase database WithPath:[self getDBPath]];

 if (![db open]) 
 {
 NSLog(@"Could not open db.");
 [ pool release];
 }

 //get users
 FMResultSet *rs = [db executeQuery:@"SELECT * FROM R order by date desc"]; //query provides result set

 //create result array
 NSMutableDictionary *myDictionary = [[NSMutableDictionary alloc] init];

 while ([rs next])
 {
 NSMutableArray *usersDictArray = [NSMutableArray array];

 //look up names for id's
 [usersDictArray addObject:[rs stringForColumn:@"rNames"]];
 [usersDictArray addObject:[rs stringForColumn:@"dName"]];
 [usersDictArray addObject:[rs stringForColumn:@"date"]];
 [myDictionary setObject:usersDictArray forKey:[rs stringForColumn :@"rID"]];

 [usersDictArray release];
} 

 //return usersArray;
 return myDicti onary;

 [myDictionary release];

 [pool drain];
}

-(NSMutableDictionary *)loadHistoryFromDBExtended {
 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

 FMDatabase* db = [FMDatabase databaseWithPath:[self getDBPath]];

 if (![db open]) 
 {
 NSLog(@"Could not open db.");
 [ pool release];
 return nil; // I'm assuming you should return nil here
 }

 //get users; query provides result set
 FMResultSet * rs = [db execut eQuery:@"SELECT * FROM R order by date desc"];

 //create result array
 NSMutableDictionary *myDictionary = [[NSMutableDictionary alloc] init];

 while ([rs next])
 {
 NSMutableArray *usersDictArray = [NSMutableArray array];
 //look up names for id's
 [usersDictArray addObject:[rs stringForColumn: @"rNames"]];
 [usersDictArray addObject:[rs stringForColumn:@"dName"]];
 [usersDictArray addObject:[rs stringForColumn:@"date"]];
 [ myDictionary setObject:usersDictArray forKey:[rs stringForColumn:@"rID"]];
 // [usersDictArray release];
} 
 [pool drain];
 return [myDictionary autorelease ];
)

I am trying to fix the EXC_BAD_ACCESS error thrown when I access the NSMutableDictionary in the tableView: cellForRowAtIndexPath: indexPath. Now, when I use the method loadHis When toryFromDBExtended fills in ridesDict, it works normally:

self.ridesDict = [self loadHistoryFromDBExtended]; 

NSLog(@"rides dict %@", self.ridesDict);

However, I don’t want to call [self loadHistoryFromDBExtended] for each unit being loaded, because the dictionary will not change so I try to move:

self.ridesDict = [self loadHistoryFromDBExtended];

to viewDidLoad, now I receive an EXC_BAD_ACCESS error when I use it:

NSLog (@"rides dict %@", self.ridesDict);

In tableView: cellForRowAtIndexPath: indexPath. From what I can see, it seems that I have some memory retention/release issues, but I can’t seem to Figured it out. After calling the loadHistoryFromDBExtended method, I tried [self.ridesDict retain] in viewDidLoad, but it did not help. I am very new to this, so I appreciate any suggestions on where to go.

Edit: This is the loadHistoryFromDBExtended method:

-(NSMutableDictionary *)loadHistoryFromDBExtended
{ 
 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];< br />
 FMDatabase* db = [FMDatabase databaseWithPath:[self getDBPath]];

 if (![db open]) 
 {
 NSLog(@" Could not open db.");
 [pool release];
 }

 //get users
 FMResultSet *rs = [db executeQuery:@"SELECT * FROM R order by date desc"]; //query provides result set

 //create result array
 NSMutableDictionary *myDictionary = [[NSMutableDictionary alloc] init];

 while ([rs next])
 {
 NSMutableArray *usersDictArray = [NSMutableArray array];

 //look up names for id's
 [usersDictArray addObject:[rs stringForColumn:@"rNames"]];
 [usersDictArray addObject:[rs stringForColumn:@"dName"]];
 [usersDictArray addObject:[rs stringForColumn:@"date"]];
 [myDictionary setObject:usersDictArray forKey:[rs stringForColumn:@"rID"]]; 

 [usersDictArray release];
} 

 //return usersArray;
 return myDictionary;

 [myDictionary release] ;

 [pool drain];
}

There are many questions about how to implement this method. After checking whether it can be When opening the database, release the auto-release pool, and then continue to execute the rest of the code. I think you might want to return nil at that time. In the [rs next] section, you will create an NSMutableArray with an array, which creates an auto-released object. Therefore, you should not call [usersDictArray release] because of this Will be over-released. (In each cycle, "temporary", automatically released usersDictArray instance will be stored in the pool auto-release pool. When you call [pool drain], the auto-release pool will send a release message to all these temporary instances ). Near the end, you return to myDictionary;, which will never touch the next two lines. Therefore, the auto-release pool you created will never be released (popped).

This It may be the way I implemented it:

-(NSMutableDictionary *)loadHistoryFromDBExtended {
 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
< br /> FMDatabase* db = [FMDatabase databaseWithPath:[self getDBPath]];

 if (![db open]) 
 {
 NSLog(@"Could not open db .");
 [pool release];
 return nil; // I'm assuming you should return nil here
 }

 //get users; query provides result set
 FMResultSet *rs = [db executeQuery:@"SELECT * FROM R order by date desc"];

 //create result array
 NSMutableDictionary *myDictionary = [ [NSMutableDictionary alloc] init];

 while ([rs next])
 {
 NSMutableArray *usersDictArray = [NSMutableArray array];
 //look up names for id's
 [usersDictArray addObject:[rs stringForColumn:@"rNames"]];
 [usersDictArray addObject:[rs stringForColumn:@"dName"]];
 [usersDictArray addObject:[rs stringForColumn:@"date"]];
 [myDictionary setObject:usersDictArray forKey:[rs stringForColumn:@"rID "]];
 // [usersDictArray release];
} 
 [pool drain];
 return [myDictionary autorelease];
}

(Please note, how I achieve this assumes that the reason behind creating a local autorelease pool is to improve performance, and there is a global NSAutoreleasePool to absorb the final [myDictionary autorelease] autorelease object).