What is the difference between UIViewController and UITableViewController

Question

Sometimes I want to subclass UIViewController for some app wide customizations. Eg. something that all view controllers should perform during viewDidLoad or viewWillAppear or so

Answer 1

I believe all of the behavior UITableViewController adds is well defined in the class documentation: https://developer.apple.com/documentation/uikit/uitableviewcontroller?language=objc

The UITableViewController class creates a controller object that manages a table view. It implements the following behavior:

• If a nib file is specified via the initWithNibName:bundle: method (which is declared by the superclass UIViewController), UITableViewController loads the table view archived in the nib file. Otherwise, it creates an unconfigured UITableView object with the correct dimensions and autoresize mask. You can access this view through the tableView property.

• If a nib file containing the table view is loaded, the data source and delegate become those objects defined in the nib file (if any). If no nib file is specified or if the nib file defines no data source or delegate, UITableViewController sets the data source and the delegate of the table view to self.

• When the table view is about to appear the first time it’s loaded, the table-view controller reloads the table view’s data. It also clears its selection (with or without animation, depending on the request) every time the table view is displayed. The UITableViewController class implements this in the superclass method viewWillAppear:. You can disable this behavior by changing the value in the clearsSelectionOnViewWillAppear property.

• When the table view has appeared, the controller flashes the table view’s scroll indicators. The UITableViewController class implements this in the superclass method viewDidAppear:.

• It implements the superclass method setEditing:animated: so that if a user taps an Edit|Done button in the navigation bar, the controller toggles the edit mode of the table.

All of these are behaviors which should be easy to re-implement if they apply to your specific controller and table view.

In general I have found it preferable to implement these behaviors myself in order to allow for alternate inheritance hierarchies as you noted and because I usually consider setting both the delagate and datasource of a table view to be a view controller a design smell. Those are independent concerns which usually can and should be handled by some other class (e.g. a dedicated data source for a particular model class) rather than bloating a view controller.