objective c - BAD_ACCESS error -

in h file have

@property __strong ghost* **gameboard; 

and initialized in m file this

sharedengine.gameboard = (ghost* __strong** )malloc(sizeof(ghost**) * [levelmanager sharedmanager].selectedlevel.fieldrowsnumber);     for(int = 0; < [levelmanager sharedmanager].selectedlevel.fieldrowsnumber; i++ )     {         sharedengine.gameboard[i] = (ghost* __strong*)malloc(sizeof(ghost*) * [levelmanager sharedmanager].selectedlevel.fieldcolumnsnumber);     } 

have done wrong because having bad_access crashes.