Question

I have a variable in a class, NSNumber. I want to pass the value of this var to another class var. The problem is that I release the object of the first class and obtain an error message when I try to set the value of the second class var.

In C++ this is so easy to do. But here with memory management and pointers confused me so much.

Solution code, for testing:

#import <Foundation/Foundation.h>
@interface A : NSObject 
{
    NSNumber *a;
}

@property (nonatomic, retain) NSNumber *a;

@end

int main(int argc, char *argv[]) 
{
    NSAutoreleasePool *p = [[NSAutoreleasePool alloc] init];

    A *instance1 = [[A alloc] init];
    A *instance2 = [[A alloc] init];

    [instance1 setA:[NSNumber numberWithFloat:5.43f]];

    instance2.a = [instance1.a copy];
    [instance1 release];

    NSLog(@"Valor de la que sigue viva, parte2: %@", instance2.a);


    [instance2 release];
    [p release];
    [pool drain];

    return 0;
}

Answer 1

You should use a retain property or copy the instance variable:

@interface A {
 NSNumber *a;
}

@property (nonatomic, retain) NSNumber *a;
@end

...
A *instance1 = [[A alloc] init];
A *instance2 = [[A alloc] init];

instance1.a = instance2.a;
//or
instance2.a = [instance1.a copy];

Read some docs about retain-counted memory management which is what Objective-C uses.