Question

I have some doubt regarding retain in .h file. I know that if we alloc/copy/retain than we need to release it, but in following case

@property (nonatomic, retain) IBOutlet UITableView *myTable;

Do I need to release this table view object in my dealloc. I have created this tableview using xib.

Thanks.

Answer 1

So sayeth the docs:

Objects in the nib file are created with a retain count of 1 and then
autoreleased. As it rebuilds the object hierarchy, however, UIKit
reestablishes connections between the objects using the
setValue:forKey: method, which uses the available setter method or
retains the object by default if no setter method is available. If you
define outlets for nib-file objects, you should always define a setter
method (or declared property) for accessing that outlet. Setter
methods for outlets should retain their values, and setter methods for
outlets containing top-level objects must retain their values to
prevent them from being deallocated.

And:

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.

So basically, when being loaded from a NIB/XIB, the property is used. Meaning, if you specify retain properties on your IBOutlets (which you should), you need to release them. The preferred way to do this is in viewDidUnload, using the property.

@property (nonatomic, retain) IBOutlet UITableView *myTable;

...

- (void) viewDidUnload
{
    self.myTable = nil;
}