Question

Maybe it is a dumb question but I would like to know when we have to or when it is recommanded to create new class. This is not really clear in my mind. For now, I’ve only one class per Controller and that’s it… All my code is in this class.
I think it could be better…

Regards

Answer 1

If you’re following the MVC pattern, for the most part your classes should be separated into one of those categories:

• Controllers: UIKit/NS view controllers, which are responsible for presenting views and receiving messages from interactive elements on those views.
• Views: If the view presented by one of your controllers requires a lot of custom logic in order to present itself, it might be a better idea to separate it into its own class. In essence, this is done when creating views using Interface Builder (.xib files).
• Models: Objects that encapsulate logic in your application.

For example, if you are building an RSS viewer according to this design pattern, you’d likely make the following classes:

• Models representing an individual RSS item, as well as one that represents an RSS feed. If you roll your own RSS feed parser, you would want to isolate the logic required to fetch entries within another class.
• Controllers to handle displaying the feed and individual views. Controllers should only be concerned with presenting data. In the case of an RSS viewer on iOS, you would likely use a UINavigationController with a root view controller of the UITableViewController class. Tapping on a table cell pushes another UIViewController responsible for displaying an individual RSS item.
• While the UITableController has a default view to display a list of items, the individual item likely needs custom logic to be displayed well. You might want to create a view class or .xib to present these. The UIViewController is responsible for populating data on the view (setting values on IBOutlets on the .xib, etc).

As a general guideline, you should try to adhere to the single responsibility principle–every class should have a single responsibility, and it can perform its tasks more or less autonomously.

In this vein, controllers are responsible for handling the display of a single kind of view and for delegating messages from that view. Views are responsible for displaying data. Models are responsible for the singular purpose they were created for–an RSS item for mapping data from an RSS feed to an object, an RSS feed object for managing a group of RSS items (adding, removing, possibly fetching more via an NSURLRequest).

Note: Your question is a bit vague according to Stack Overflow guidelines, so that may be why it is being down-voted. Consider adding a specific example or description of the dilemma you’re facing.