Question

Hey all, trying to learn objective-c. It was going quite well, until I realized I was missing a link.

When building in the spirit of MVC, I understand it as you Model and View should never talk to eachother.

I have this problem I’m messing around with now.

• A model containing a polygon class.
  Contains an polygon object with
  attributes like numberOfSides.

• A controller, reading some UI
  elements and modifying the model. For
  example numberOfSides.

• A view, containing a view drawing
  polygons.

Now, this is where the trouble arose. The view needs information about the object from the model. How do I get that? I tried some IBOutlet, but never got it to work.

I ended up creating a property for the view which could contain numberOfSides. Then I would a controller method which would call a view method back and set the numberOfSides.

I hope some of you can clarify this a bit for me and tell me how you should go ahead with this.

Thanks a bunch and goodnight! 🙂

Answer 1

MVC in Cocoa is slightly different than traditional MVC, so I’ll answer with the Cocoa way.

You’ve got a controller object, which has a pointer to your Polygon object. Your controller should also have a pointer to your View (via an IBOutlet, most likely). As the polygon changes (whether numberOfSides or whatever), the controller needs to be aware of that and relay the information on to the view. Likewise, if the view is allowed to change the numberOfSides (say you have a slider to increase the number of sides), then the controller needs to be aware of that change and pass it to the Polygon object.

Basically, the purpose of the controller is to pass information back and forth from the view to the model and make sure that they stay synchronized.