Every tutorial I read about data binding / NSArrayController told to set the Mode and the Keys in the Object Controller (Attributes Inspector) for the data model class I use. Why do I have to do this?
In my sample application I create all objects in code and add them to the array controller in code too. The program still works fine without any settings in the Object Controller. I use the NSCollectionView to present my data.
To answer the question in the subject, the Object Controller section lets you determine what the array controller is controlling. In your screenshot the array controller is controlling objects of a Person class. But the array controller can also control a Core Data entity. That's what the Mode menu is for. The keys are pieces of the object/entity the array controller is controlling.
The reason the tutorials tell you to set the mode and keys is they are demonstrating using NSArrayController with Cocoa bindings. You must set the mode and keys so you can bind the array controller to the collection view in Interface Builder and have the collection view display relevant data from the array controller. If you are writing code to do all the NSArrayController work and not using Cocoa bindings, you can avoid setting the mode and keys.
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This question may not have a straight answer, but I am curious as to what others think. I have a UIViewController and inside that I have 2 objects a UIView and and UITableView. Each object as it's own custom class. My question is about the UITableView, what object should be the datasource and the delegate. Right now I have the UIViewController set to those rolls, but is it beset practice to set the object itself to be the data source and the delegate, maybe use the method awakeFromNib to set those 2 sources. Are both ways ok? I would think that setting the data and the delegate to the class that represents the tableview would keep that code apart from the view controller, which I would think would be a good thing.. but maybe not...
Good question actually.
Look at the Controller as an example of the Mediator Pattern from the Gang of Four: it's mediating the relationship between the View and the Model. Most of the web world has gone to using binding of some sort, so you typically see model objects 'bound' directly to the view layer, e.g. a text edit field might have an expression indicating which field in the domain object it is editing, then the framework will provide the services of marshaling and unmarshaling that data.
In Cocoa, you typically don't do that: you bind to properties in the Controller, and those typically are then used to transform the underlying domain class. So for instance, if you make a storyboard and make a form and have a custom controller, now you want to edit the name of some entity, e.g. User, you would CTRL-drag from the edit box over to the source, it would make an outlet, which would then give you control not only of what appears in that box, but the control itself. Then you could add a submit button and CTRL-drag to create a method, for Save, and when that's clicked, you could update the underlying User instance.
If I am using an instance of NSArray to populate a pop-up button, where in terms of MVC does that NSArray need to be initialised? I'm guessing it would fall under Model, however if that's the case, how do I initialise the array? Do I start a new implementation file to contain the array? (Obviously don't want to use my app delegate file as that would fall under Controller, not Model.)
The "model" part of MVC is the data that the app stores, presents, and/or allows the user to manipulate. It would largely be the same whether your app was running on a Mac, an iPhone or whatever. The "view" is the UI. That is the things the user actually sees on screen. The controller is the part that goes in between these two. It's responsible for implementing the specific behavioral logic for the app as well as "gluing" the view layer to the model layer.
So, with that said, the array of items to be displayed in a popup button may or may not be part of the model. It entirely depends on the specific UI you're implementing. If the selection is between a number of objects represented in the model, the array's contents would indeed be part of the model, but it still might be that the controller pulls the items out of the model in another form and turns them into an NSArray. It might also be a way to select between e.g. a fixed list of actions to be performed, in which case it's more properly part of the controller layer itself.
In other words, there's no one answer to your question. But, the likelihood is that the controller will at least provide the array in question to the UI, and may also be entirely responsible for its content. It all depends on exactly what you're trying to accomplish.
The initialization would happen within the model object, but that initialization would likely be called from a view controller (I wish these were just called controllers--there's no ModelController class.) Possibly in viewDidLoad but really wherever the best fit for your use case would require.
The model object should initialised by the controller object, usually in the viewDidLoad method. If a model object is owned by another model object (for example, if your custom model object has an NSArray instance variable, then your custom object is the parent and the NSArray is the child), then that child model object should be initialised in the initialised method of the parent model object.
I suppose your NSArray is a model object on its own, so it should be initialised in the viewDidLoad method of the controller object.
This is just one answer and not necessarily how everyone develop applications in objective C.
If I have an app with a small data model or with models scoped to their views, I will put the models on the AppDelegate or in the viewControllers themselves, if they are limited in scope to that view.
They will be initialized closest to where it makes sense in the app for that data.
Sometimes you will see a "FAT" viewController which represents a home screen controller or main screen controller and folks will pile the models on that class. Its very common.
But if I have an application with a large data model - lots of models that have lifetimes not scoped to the life of a view - then I will create a class in my application called *myAppNameHere*AppModel, and I will centralize the storage of application models, and use service classes as necessary to request data to populate/update models.
This is just one approach. And great question!
I'm developping a little DB book management Mac OSX app with CoreData and DataBindings.
I have a TableView with all the book authors.
I would another TableView that rapresent all books written by the author selected in the previous table...
The both tables are managed with two ArrayController in IB.
My problem is that I don't know how to filter the second table / ArrayController with the first table selection.
I must also insert a new book in the filtered ArrayController.
I can do it?
Thanks a lot!
I actually wrote a tutorial that might be of help http://themikeswan.wordpress.com/2009/05/22/7/ the short answer is that you bind the array controller for the book table to get it's Content Set from the selection of the other array controller. The book array controller would then get it's items from whichever author is selected in the author array controller. You should also just have to add a button for adding books and connect it to the book array controller's add: method (I have not tried this as of yet, but in theory it should work, I'm not sure if the author relationship will get properly set though).
You should read about NSPredicate, array controllers supports them for filtering the content. To add a new book you should override "add:" method of the ArrayController (subclass it) or write a custom method somewhere in the window controller that will construct new object and push it into the ArrayController with addObject: call.
I'm setting up an edit window for a player to edit his user data. I've got all of the fields on the edit form bound to the appropriate Core Data entity (via an NSArrayController), and I've got an awakeFromNib method installed to handle calling the record, but I'm not sure what to put inside the method to get the record to display.
Ultimately, my goal with this is to set it up so that the application checks whether an entry exists for the user, and create one for him if there's no entry in the table.
You should look at using a NSObjectController or NSArrayController rather than binding directly to the NSManagedObject. The controllers work properly with bindings and your data will display nicely and changes you make will be propagated via the controller to your NSManagedObject.
You can set the object used by the controller in your awakeFromNib. On NSArrayController use the setSelectionIndex:(NSUInteger) index message and then to avoid empty selection send it the setAvoidEmptySelection:TRUE message
Hope that helps.
I'm having trouble converting my Cocoa project from a manually-synched interface model to a bindings model so that I don't have to worry about interface glue code.
I followed the CocoaDevCentral Cocoa Bindings tutorial to make sure that I had covered all the bases, but things aren't working correctly. I have a master-detail interface, but I'm having trouble even getting the master portion of the interface to work correctly. No data is showing up in the master column, even though I've set up the bindings model similar to how it is shown in the tutorial. I've made sure all my controllers and objects have -(id)key and -(void)setKey:(id)key methods so that they're bindings-compliant, I've created a ControllerAlias object in my nib, connected it to my controller, created an NSArrayController that binds to one of the NSMutableArrays from the class that ControllerAlias connects to, made sure to set the type of objects that are contained within the array, and then I've bound a table column to the NSArrayController.
I'm getting no errors whatsoever in the Console, and setting NSBindingDebugLogLevel to 1 doesn't produce any errors either, that would help me figure out what the problem is.
The only other thing I could think of to make sure that things are working correctly is to check that the NSMutableArray that connects to the NSArrayController actually has something in it, and it does.
Any suggestions? What other typical pitfalls are there with Cocoa bindings that I should check?
Have you put a breakpoint in your key: method to determine if it is getting called or not? If it isn't, then that would indicate that something isn't set up correctly for the binding in the table column (since you have verified that your array does have items in it).
I don't think that you need to create an Object Controller anymore (that tutorial is a bit out of date). Just create an Object in your NIB, and set its class to your Controller class. You can set up the bindings directly through it instead of the ObjectController.
To set up a binding, I do the following:
Create an instance of my controller in the NIB.
Create an NSArrayController, bind it to an array in my controller.
For each column in the table, bind the value to a member of an object in the array controller.
That should be all that you need to do - I think they've cleaned this up quite a bit since bindings were first introduced a few versions ago.
I've created a ControllerAlias object in my nib,
What is a “controller alias”? Is this a model, controller, or view?
connected it to my controller,
What do you mean?
created an NSArrayController that binds to one of the NSMutableArrays from the class that ControllerAlias connects to,
Classes don't have NSMutableArrays.
What property of the array controller did you bind?
What object did you bind it to?
What key path of that object did you bind it to?
… and then I've bound a table column to the NSArrayController.
What property of the table column did you bind?
Which property (key path) of the array controller did you bind it to?
So in my original code, I was modifying the array (which the NSArrayController was representing) in awakeFromNib, not in init, so the changes weren't being reflected in the interface since I wasn't modifying the array via a key-value observing method.
I changed the code from
theArray = [[NSMutableArray alloc] init];
[theArray addObject:newThing];
to:
theArray = [[NSMutableArray alloc] init];
NSMutableArray *bindingsCompliantArray = [self mutableArrayValueForKey:#"things"];
[bindingsCompliantArray addObject:newThing];
I think the other solution is to do the loading in the -(id)init method instead of the -(void)awakeFromNib method, but that required a larger refactor, so I didn't do that.
I figured this out by adding a button to create a new thing in the array list via the NSArrayController, and when I clicked the button, a new thing was added to the array and my existing array magically showed up as well.