I am newbie to iPhone programming. I am not using Interface Builder in my programming. I have some doubt about memory management, @property topics in iPhone. Consider the following code

@interface LoadFlag : UIViewController {

UIImage *flag; UIImageView *preview;

}

@property (nonatomic, retain) UIImageView *preview;
@property (nonatomic, retain) UIImage *flag;    

@implementation
@synthesize preview;
@synthesize flag;

 - (void)viewDidLoad
   {
     flag = [UIImage imageNamed:@"myImage.png"]];
     NSLog(@"Preview: %d\n",[preview retainCount]); //Count: 0 but shouldn't it be 1 as I am retaining it in @property in interface file
     preview=[[UIImageView alloc]init];
     NSLog(@"Count: %d\n",[preview retainCount]); //Count: 1 
  preview.frame=CGRectMake(0.0f, 0.0f, 100.0f, 100.0f);
  preview.image = flag; 
  [self.view addSubview:preview];
  NSLog(@"Count: %d\n",[preview retainCount]); //Count: 2
  [preview release];
         NSLog(@"Count: %d\n",[preview retainCount]); //Count: 1
   }

1. When & Why(what is the need) do I have to set @property with retain (in above case for UIImage & UIImageView) ? I saw this statement in many sample programs but didn't understood the need of it.

2. When I declare @property (nonatomic, retain) UIImageView *preview; statement the retain Count is 0. Why doesn't it increase by 1 inspite of retaining it in @property.

3. Also when I declare [self.view addSubview:preview]; then retain Count increments by 1 again. In this case does the "Autorelease pool" releases for us later or we have to take care of releasing it. I am not sure but I think that the Autorelease should handle it as we didn't explicitly retained it so why should we worry of releasing it.

4. Now, after the [preview release]; statement my count is 1. Now I don't need UIImageView anymore in my program so when and where should I release it so that the count becomes 0 and the memory gets deallocated. Again, I am not sure but I think that the Autorelease should handle it as we didn't explicitly retained it so why should we worry of releasing it. What will happen if I release it in -(void) dealloc method

5. In the statement -> flag = [UIImage imageNamed:@"myImage.png"]]; I haven't allocated any memory to flag but how can I still use it in my program. In this case if I do not allocate memory then who allocates & deallocates memory to it or is the "flag" just a reference pointing to -> [UIImage imageNamed:@"myImage.png"]];. If it is a reference only then do i need to release it.

Thanks in advance.