Question

What I did is

int main(int argc, char *argv[]){
    NSString *str = [[NSString alloc] init];
    str = @"a a a a a a a a a ";
    [str release];
    NSLog(@"string is %@",str);
    return 0; 
}

I think string will be nil because we release it before printing it. However, it is not. Therefore, my consumption is wrong.

Can anybody advice me and correct me. Any comments are welcomed. Thanks

Answer 1

NSString *str = [[NSString alloc] init];

This declares a variable that is a pointer to an instance of NSString, allocates memory for an instance of NSString, initialises that memory, then assigns a pointer to that memory to the variable you declared.

str = @"a a a a a a a a a ";

This creates an NSString constant and assigns a pointer to it to the variable that you declared. As you no longer have a reference to the original NSString object you created, you have leaked the memory you allocated for it.

[str release];

This declares that this code no longer wishes to be an owner of the memory allocated to str. As you created it with a string literal, this object will always exist in your program, and releasing it does nothing.

I think string will be nil because we release it before printing it.

Releasing an object does not ever set it to nil.