UIViewController memory management

Hi I have a very basic issue of memory management with my UIViewController (or any other object that I create); The problem is that in Instruments my Object allocation graph is always rising even though I am calling release on then assigning them nil.

I have 2 UIViewController sub-classes each initializing with a NIB; I add the first ViewController to the main window like [window addSubView:first.view]; Then in my first ViewController nib file I have a Button which loads the second ViewController like :

-(IBAction)loadSecondView{
     if(second!=nil){ //second is set as an iVar and @property (nonatomic, retain)ViewController2* second; 
         [second release];
         second=nil;
     }
     second=[[ViewController2 alloc]initWithNibName:@"开发者_Python百科ViewController2" bundle:nil];
     [self.view addSubView:second.view];

}

In my (second) ViewController2 i have a button with an action method

-(IBAction) removeSecond{

    [self.view removeFromSuperView];
}

Please let me know if the above scheme works in a managed way for memory...? In Instruments It does not show release of any allocation and keeps the bar status graph keeps on rising.

---

First of all, why use this scheme when second is a property:

if(second!=nil){
     [second release];
     second=nil;
 }
 second=[[ViewController2* second]initWithNibName:@"ViewController2" bundle:nil];

A propery automatically releases it's old value when the setter is used. So this could be rewritten as:

if(self.second == nil) { //Prevents creating a new controller if there already is one.
     self.second = [[[ViewController2 alloc] initWithNibName:@"ViewController2" bundle:nil] autorelease];
}

Also, what's up with [ViewController2* second]? Why is that asterisk there, and what does the class method second do?