Here is how I'm solving a similar problem: I wanted to:
create reusable, self-contained "widget module classes" implementing a complex view built from multiple UIKit components (and other nested widget module classes!). The higher-level customer classes of these widget classes don't care about what's a UILabel, what's a UIImageView internally within the widget, the customer classes only care about concepts like "displaying the score" or "showing the team logo."
within a widget module class, lay out the UI for the widget and hookup outlets using interface builder
for higher level customers of a widget, I wanted to be able to place the frame of the widget within the view of the customer in interface builder without having to design custom plugins to IB, etc.
These widgets are not top level controllers: so it makes no sense for them to be subclasses of UIViewController. Then also there's the Apple advice not to have more than one VC on a visible screen at a time. Also, there's so much advice and opinion floating around like "MVC! MVC! You must separate your View and your control! MVC!" that people are so strongly discouraged from subclassing UIView or ever placing app logic within a UIView subclass.
But I decided to do it anyway (subclass UIView). I've been around the block a few times (but fairly new still to the iPhone SDK/UIKit), and I'm very sensitive to design that is ugly, and that can cause problems, and I frankly don't see the problem with subclassing UIView and adding outlets and actions. In fact there are many advantages to making your reusable widget be a subclass of UIView rather than be UIViewController-based:
You can place a direct instance of the widget class in a customer view's interface builder layout, and the widget view's UIView frame will be properly initialized when the customer class is loaded from the xib. This is much cleaner to me than putting a "placeholder view" in the customer, then instantiating the widget module programmatically, and setting the widget's frame to that of the placeholder, and then swapping the placeholder view for the widget's view.
You can create a clean and simple xib file to lay out the widget's components in interface builder. The File's Owner is set to your widget class. The nib file contains a root (vanilla) UIView where all of the GUI is laid out, and then in the awakeFromNib: method of the widget, this nib view is added to the widget itself as a subview. Any frame size adjustments can be handled here, entirely within the widget code, if any is necessary. Like so:
- (void) awakeFromNib
{
[[NSBundle mainBundle] loadNibNamed:@"MyWidgetView" owner:self options:nil];
[self addSubview:self.view];
}
- The widget self-initialzes its user interface by using NSBundle's loadNibNamed:owner:options method in its own awakeFromNib method, so integration of the widget into customer classes is clean: just drop a UIView into the customer's view in IB, change the UIView's class to MyWidgetView, and in the customer's init or viewDidLoad set up any defaults in the widget's display using the widget's API that you write yourself (setScore: setTeamImage: etc.)
It seems to me there is essentially no difference in the resulting code between subclassing a UIView in this way to make a reusable "widget", and using a UIViewController. In both cases the .h files contain widget class members, outlets, action declarations, and special API declarations. In both cases the .m file contains action implementations, and special API implementation. And the view IS separated from the control -- the view is in the xib file!
So, in summary, this is what I do for packaging up complex reusable view widgets:
- Make the widget class a subclass of UIView
- Instantiate the widget wherever you want, in other views in your app in IB directly by dragging a UIView from the tools library, and changing the class to your "MyWidgetClass."
- Design your widget's UI in IB in a nib inside a root vanilla UIView.
in the widget class's awakeFromNib: method, load the widget's UI from xib and do
[self addSubview:self.theXibRootView]
Code the widget just like you would a UIViewController: outlets, actions, special APIs
I'd be interested in hearing about other structural systems for creating reusable widgets, and what the advantages are over this approach.
If the widget needs to report events to the customer class, just use a delegate protocol where the customer sets the widget's delegate to self, just like in a UIViewController.
Apple introduced the concept of "storyboarding" in iOS5 SDK to simplify and better manage screens in your app. You can still use the .xib way of development.
Pre-storyboard, each UIViewController had an associated .xib with it. Storyboard achieves two things:
.storyboard is essentially one single file for all your screens in the app and it shows the flow of the screens. You can add segues/transitions between screens, this way. So, this minimizes the boilerplate code required to manage multiple screens.
Minimizes the overall number of files in an app.
You can avoid using Storyboard while creating a new project by leaving the "Use Storyboard" option unchecked.
You could refer this tutorial to get started.
Best Answer
The rule of thumb I use, is auxiliary objects can be put in if they are related to the UI being defined in the nib in some way - so either proxy objects that hold references to elements or actions that get triggered.
Proxy methods all get wired in when loading the nib and pass in the already created object via the userinfo dictionary you can optionally pass in along with the nib name.
There's nothing at all wrong though I think, in a purely logical nib that would use the target/action system to wire up multiple proxy objects. That might be easier than doing all the wiring in code, though I've not seen that used in practice.