objective-c - 正确使用FMDB/内存

Question

我在类似的问题中找不到解决我的问题的方法。我正在使用 fmdb 包装器从 sqlite 数据库中提取一大堆数据。我的 fmdb 实用程序类中有一个与此类似的方法:

  - (NSMutableArray *) getConnectionsForKey: (NSString *) key
 {

     NSString *query = [NSString stringWithFormat:@"select * from user" ];



     FMResultSet *results = [database executeQuery:query];

     NSMutableArray *retArray = [[ NSMutableArray alloc ] init ];

     while ([ results next ]) {

         NSString *fname = [ results stringForColumn:@"firstname" ];
         NSString *lname = [ results stringForColumn:@"lastname" ];


         NSMutableDictionary *aDictionary = [[ NSMutableDictionary alloc ]
                                               init
                                             ];

        [ aDictionary  
          setObject:fname 
          forKey:@"firstname" 
        ]; 

       [ aDictionary 
        setObject:lname 
        forKey:@"lastname" 
       ];



       [ retArray addObject:aDictionary ];

       [ aDictionary release ];


}

[ results close ];

return retArray;
}

它将我的信息存储在一系列字典中。在我的 View Controller 中，我像这样调用我的方法:

 -(void) setCurrentConnections: (NSString *) key {

   if ( currentConnections != nil ) {
         [ currentConnections removeAllObjects ];
   }

   LocalDatabase *db = [[ LocalDatabase alloc ] init ];

   [ db openDatabase ];

   currentConnections = [ db getConnectionsForKey:key ];

   [ db closeDatabase ];
  [ db release ];


}

现在，每次我调用此方法用新联系人更新我的数组时，我都会遇到一致的泄漏，正如我使用分配工具观察到的那样，泄漏不断增加。即使我在从数据库加载后立即释放 currentConnections 并且不再调用此方法，也会发生这种情况，所以我怀疑这是数据库实现的问题。有其他人解决过这个问题吗？

Answer 1

“setCurrentConnections”中的 currentConnections 发生泄漏。这是我修复它的方法(请注意，我还更改了“getConnectionsForKey”以返回自动释放的对象)。

 - (NSMutableArray *) getConnectionsForKey: (NSString *) key
 {

     NSString *query = [NSString stringWithFormat:@"select * from user" ];
     FMResultSet *results = [database executeQuery:query];

     NSMutableArray *retArray = [[ NSMutableArray alloc ] init ];
     while ([ results next ]) {

         NSString *fname = [ results stringForColumn:@"firstname" ];
         NSString *lname = [ results stringForColumn:@"lastname" ];
         NSMutableDictionary *aDictionary = [[ NSMutableDictionary alloc ] init];

        [ aDictionary  
          setObject:fname 
          forKey:@"firstname" 
        ]; 

       [ aDictionary 
        setObject:lname 
        forKey:@"lastname" 
       ];

       [ retArray addObject:aDictionary ];
       [ aDictionary release ];


       }

[ results close ];

return [retArray autorelease];
}


 -(void) setCurrentConnections: (NSString *) key {

   [ currentConnections removeAllObjects ];
   [ currentConnections release];

   LocalDatabase *db = [[ LocalDatabase alloc ] init ];

   [ db openDatabase ];

   currentConnections = [ db getConnectionsForKey:key ];
   [currentConnections retain];

   [ db closeDatabase ];
  [ db release ];

}

您也许可以跳过对 removeAllObjects 的调用，而只调用release。原始代码中的问题是您覆盖了对现有 currentConnection 的引用，而没有先释放它，因此导致了泄漏。