Question

I have a custom class:

 @interface Player : NSObject {
   NSInteger mPlayerNo;
 }

 -(id) initWithNum:(NSInteger) playerNum;

 @implementation Player

 -(id) initWithNum:(NSInteger) playerNum
 {
   if(![super init])
   return nil; 
   ... 
   mPlayerNo=playerNum;
   return self;
 }

 @end

I need the array of the Player objects in the other programm class:

 @interface Spec : NSObject  {
    NSMutableArray * mPlayers;
    ...
  }

So, I am trying to fill mPlayers arr in the init method of the Spec class like this:

- (id)init {
   if(![super init])
      return nil; 
   NSMutableArray * _array=[[NSMutableArray alloc] init];
   mPlayers=_array;
   [_array release];
   Player * _player=[[[Player alloc] initWithNum:(NSInteger)1]autorelease];
   [mPlayers addObject:_player]; // crashes with EXC_BAD_ACCESS

It doesn’t work. But if I change

   NSMutableArray * _array=[[NSMutableArray alloc] init];
   mPlayers=_array;
   [_array release];

with

   mPlayers=[[NSMutableArray array]retain];

All works fine.
It is something strange for me. Please, help to understand the problem with alloc init.

Answer 1

The problem is that you’re releasing your array before using it.

NSMutableArray * _array=[[NSMutableArray alloc] init]; //Retain count of 1

mPlayers=_array; //Still 1.
//Adding a new pointer to the same object doesn't affect the object's retain count.

[_array release]; //Now it's 0. Array is gone!