How to retain this object when inserting to mutable array?

Question

update: I have found the bug in my copyWithZone method in A. Thanks everyone.

update: sorry, I do have the @properties declared, I thought it was obvious so I skipped them in my OP. Sorry about that.

The crash message is: objA was released (zombie) memory when trying to access the str.

---

My data structure looks like this:

@class A
{
   NSString *str;
}
@property (retain) NSString *str;  // str synthesized in .m


@class B
{
   A *objA;
}
@property (copy) A *objA;  // objA synthesized in .m

What I am trying to do is:

B *newB = [[B alloc] init];
[someMutableArray addObject: newB];

However, I will crash some times when I try to access like this:

B *myB = [someMutableArray objectAtIndex: index];

someLabel.text = myB.objA.str;

I guess the objA & objA.str were not retained when inserting B into the array. But I don't know how to make sure they are retrain.

Any help is appreciated

-Leo

Answer 1

You should be using properties for Class A and B:

@interface A : NSObject {
    NSString *str;
}

@property (nonatomic, retain) NSString *str;
@end

The use @synthesize str; in .m file, this will retain the str, don't forget to release the str in the dealloc method:

@implementation A 

@synthesize str;

- (void) dealloc { 
   [str release], str= nil; 
   [super dealloc]; 
}

@end;

Answer 2

You should look in to

http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocProperties.html%23//apple_ref/doc/uid/TP30001163-CH17

to learn about properties and how they manage memory.

Answer 3

你有没有尝试过：

[someMutableArray addObject: [newB copy] ];

Answer 4

At this line

someLabel.text = myB.A.str;

it should be...

someLabel.text = myB.objA.str;

Yes, also you should be using properties for the members of your class. That will retain them. Just don't forget to release in dealloc