MVC Model - Should controller access view's controls directly? - ios

Question

I'm learning iOS development stuff and what I have found in tutorials and books is that controller layer usually has access to the View's controls directly (textfields, labels etc.). Let's consider such an example:
Assume, that View has a label called lblResult and a textfield called txtDataToAnalyze. Than in controler interface we've got something like this:
#property (nonatomic, retain) IBOutlet UILabel* lblResult;
#property (nonatomic, retain) IBOutlet UITextField* txtDataToAnalyze;
and some #synthesize statements in the implementation file.
I have some experience with JavaSwing development, where most of thinks I'm writing manually without any GUI Builders, and what I usually do in MVC is to access the View's controls via getters/setter. For example: void setResult(String resString); or String getDataToAnalyze();. In that way, controller knows only what pieces of information are displayed in the view, and not how are they displayed. I think it is more flexible (it is easier to change the view layer later).
I know that iOS has some specific rules, has introduced XIB/NIB files etc so maybe my doubts are completely useless in case of iPhone/iPad development. But I am going to write some more serious application for iOS (actually "rewrite" it from Java Swing) and that's why I would like to ask you:
Do you think, I should change the way I am thinking and get accustomed to that new (for me) approach (xib files, creating GUI using drag&drop and providing controler with information about how data should be displayed in view) ?? Did you have similar doubts when starting with iOS?

Answer 1

Short answer:
Yes, I think you should definitely spend a little time getting accustomed to working with Interface Builder (IB) to make NIBs and storyboards and let IB create the IBOutlet and IBAction references for you for those controls with which you need to interact. Once you're proficient at it, you'll be impressed by your productivity in generating easily maintained code. Don't dismiss IB too quickly.
In terms of letting the controller interact directly with the IBOutlet and IBAction references, this is common practice for simple user interfaces. If you have some real world examples, post a new question with a screen snapshot and we can offer more practical guidance.
Long answer:
Part of your question seems to be driven by the apprehension in seeing view controllers that are doing detailed interaction with a view's controls. The thing is, if you want to isolate your controller from some of the implementation details of the view, then go ahead and subclass the view and put the view specific stuff in there. IB can interface with both view controller subclasses as well as view subclasses. So you can happily use IB and still isolate your view controller from some of these implementation details.
Personally, I only do this subclassing of UIView when the view hits some subjective complexity threshold (e.g. for me, that threshold is when I find myself doing some complicated animation, such as using CADisplayLink; complicated gesture recognizers, etc.). I also subclass those subviews that are logical entities of their own (e.g. UITableViewCell or UICollectionViewCell). But for simple views where I'm interacting with my model to setting a control's properties, interacting with text fields, etc., I think putting that in the view controller is fine. Having said that, if I have a lot of view-specific code in my controller which has nothing to do with the integration of my model with my view, then start subclassing the UIView and shifting the view-only code into that.
Implicit in your question is the notion of programmatically building view rather than using NIBs/storyboards. In my opinion, using Interface Builder (IB) to build your UI is much easier to develop and maintain. There might be some pedagogical value to doing a test project where you build your views programmatically, so you really understand what's going on, but after that, I think you'll find yourself quickly gravitating to storyboards. And you'll get plenty of chances to write your own non-IB code when you start doing things beyond the capabilities of the standard IB controls (e.g. complicated custom container views, etc.). There are definitely those who prefer to develop views programmatically, but I don't think you can beat the development speed and ease of maintenance of IB generated UIs.

Answer 2

I general, the controller does not know about the view, but the view knows about the controller.
The gang of four book says:
"MVC also lets you change the way a view responds to user input without changing its visual presentation. You might want to change the way it responds to the keyboard, for example, or have it use a pop-up menu instead of command keys. MVC encapsulates the response mechanism in a Controller object. There is a class hierarchy of controllers, making it easy to create a new controller as a variation on an existing one.
A view uses an instance of a Controller subclass to implement a particular response strategy; to implement a different strategy, simply replace the instance with a different kind of controller. It's even possible to change a view's controller at run-time to let the view change the way it responds to user input. For example, a view can be disabled so that it doesn't accept input simply by giving it a controller that ignores input events.
The View-Controller relationship is an example of the Strategy (315) design pattern. A Strategy is an object that represents an algorithm. It's useful when you want to replace the algorithm either statically or dynamically, when you have a lot of variants of the algorithm, or when the algorithm has complex data structures that you want to encapsulate."