Question

Should the Variables with the @property nonatomic and retain be released explicitly.

@interface MyScreenViewController : UIViewController <UIWebViewDelegate> {
    UIWebView* greetingView;
}

@property(nonatomic, retain) IBOutlet UIWebView* greetingView;

- (void)dealloc {
  [greetingView release];
}

Is release in delloc method Required ???

Answer 1

Ofcourse. YES you should release your properties with retain,copy and don’t for assign. You set the property to Nil in viewDidUnload.

- (void)viewDidUnload {
     [super viewDidUnload];

     self.greetingView = nil;
}

- (void)dealloc {
     [greetingView release],greetingView = nil;

     [super dealloc];
}

Refer memory management in UIViewController Class reference: http://developer.apple.com/library/ios/#documentation/uikit/reference/UIViewController_Class/Reference/Reference.html

Memory is a critical resource in iOS, and view controllers provide built-in support for reducing their memory footprint at critical times. The UIViewController class provides some automatic handling of low-memory conditions through its didReceiveMemoryWarning method, which releases unneeded memory. Prior to iOS 3.0, this method was the only way to release additional memory associated with your custom view controller class but in iOS 3.0 and later, the viewDidUnload method may be a more appropriate place for most needs.

When a low-memory warning occurs, the UIViewController class purges its views if it knows it can reload or recreate them again later. If this happens, it also calls the viewDidUnload method to give your code a chance to relinquish ownership of any objects that are associated with your view hierarchy, including objects loaded with the nib file, objects created in your viewDidLoad method, and objects created lazily at runtime and added to the view hierarchy. Typically, if your view controller contains outlets (properties or raw variables that contain the IBOutlet keyword), you should use the viewDidUnload method to relinquish ownership of those outlets or any other view-related data that you no longer need.