Is it possible to bind the representedObject property of a NSViewController to an NSArrayController's selection property (which is a NSManagedObject)?
[self.ressourcesViewController bind:#"representedObject" toObject:self.ressourcesController withKeyPath:#"selection" options:nil];
This always gives me the no selection placeholder for some reason!
this is possible by using the keypath selectedObjects.#lastObject !
Although i don't know how standard conform this is, since bindings are meant to synchronize view objects to controller objects. What i do is synchronizing 2 controller objects..
On the other side, using bindings just saves some code, needed instead to implement it manually via KVO and KVC.
Related
I am pretty new to Core Data and am currently working on a small (OSX) app that uses an NSTableView to organise objects. I would now like to delete a row/object with the click of a button on that targeted row.
I access the managed object within the table controller by calling [NSApp managedObjectContext] (still trying to figure out that dependency injection thing) but I can't easily delete an objectAtIndex: like I used to with the array (which has now been replaced by the core data stack, right?).
How do I identify the object to be deleted? And consequently, how can I cleanly remove it from the stack?
This is probably a really basic question but I couldn't find any resources on it. Bindings obviously don't work because the row does not get selected before the click occurs.
Any help is much appreciated!
Bindings would work, in that you could have the button's IBAction query the objectValue for the parent NSTableCellView. Once you have that objectValue, you could call the bound arrayController to delete the object, and then the cell/row would disappear.
So, if you have a tableCellView that has a delete button with an IBAction, within that IBAction, you could get the sender's superview, ensure it's an NSTableCellView, get the objectValue, and call [myArrayController removeObject:...]
As it says in the NSTableCellView class reference:
The objectValue is automatically set by the table when using bindings or is the object returned by the NSTableViewDataSource protocol method tableView:objectValueForTableColumn:row:.
This is actually a typical pattern with views in cocoa. objectValue or often representedObject are properties on the views that refer to the data model objects they represent, so if you have a view pointer from sender on the IBAction, you can get the related data model object. And if you're using bindings and a controller, you can then just have the controller remove that object.
With bindings, you will often create buttons that need IBActions attached, rather than some direct binding. But those IBActions can most definitely interact with the controller and not the view.
And with core data, array controllers are really slick vs. assuming you have to do it all programmatically.
I've got a NSCollectionView bound to my array of model objects, the NSView prototype to render items of the collection view is set up to use my custom NSView subclass.
At runtime a (generic) view is shown/instantiated in the collection view for each array element, all good.
However, I just can't figure out how to get to my array objects from the individual view instances to render the actual data that's specific to each element in the array.
I.e. how are we supposed to hook up data to the NSView prototype that is used to configure a 'cell' in the collection view?
Outlets don't seem to work for that particular view; they're all nil at runtime.
Bindings don't work with a vanilla NSView (apart from hidden and tooltip bindings for vanilla views..) - and we cannot add new bindings that would show up in IB for our NSView subclasses, can we?
Any hint appreciated!
Nevermind - I've settled with a custom NSCollectionView class overriding only
- (NSCollectionViewItem *)newItemForRepresentedObject:(id)object
to access the item view of NSCollectionViewItem instances created by super and set the required property there.
I've got a custom NSViewController that's also an NSOutlineViewDataSource. I also have a window with an NSOutlineView bound to an instance of my view controller as the data source, and the NSOutlineView bound to the view: property of the custom view controller.
The controller fills the outline view fine. However, selections within the view don't automatically update the representedObject property of the controller. The only thing that seems to trigger a change in representedObject is when I call setRepresentedObject: directly... which sort of defeats the purpose.
Any idea why that might be? representedObject is supposed to update automatically, right? Thanks in advance...
If I understand your question, you are not understanding what representedObject is for. The representedObject is the model object that represents all the data that a view controller is displaying. It is not the current selection of a view showing a collection of content. The representedObject for your custom top level view controller would be an NSArray or other collection class which contains the set of data you are displaying in your view controller. Changing the representedObject for your custom top level view controller should have the effect of swapping out for an entirely new data set if the pattern is being used correctly.
Typically the view controllers for the individual elements in a tabular type view would each have their own representedObject and this object would not change. For example if you were using an NSCollectionView each element in the view is controlled by an NSCollectionViewItem which is a subclass of NSViewController. The representedObject for each NSCollectionViewItem tells it what data to present in its little view.
NSOutlineView and its superclass NSTableView are different in that their cells are often NSCells rather than full fledged NSViews unless you choose to use them this way in Mac OS X 10.7 or newer. Even in this case, you don't typically have an NSViewController subclass managing each cell. So the view controller representedObject pattern is not used at the level of the individual element that the user would select. If what you want is to track the NSOutlineView's selection, there are many NSTableView methods that let you do this.
Relative newbie question. My app has a simple NSMutableArray of NSNumbers. (about a dozen integers) I'd like my UI to have a view displaying the numbers so that the user knows what's in the array. I want the contents of the view to be current, so I think I want a binding to the array (or its contents). Is there a simple way to do this?
I think I can figure this out if I change my model so that the NSMutableArray contains a custom class having a setter and getter to a declared property (following Lucas' YouTubtorial on NSTableView bindings), but I would think that there might be a simpler way, one that allows me to use my array of NSNumbers. I'd have to do a fair amount of editing if I have to redo my NSMutableArray. Thanks ...
You can use plain old NSNumbers (or anything else) in your model, no need to use a custom model class. However, you could create an NSValueTransformer subclass if your model data needs any special formatting for your view.
In your NIB you will have an NSTableView and an NSArrayController.
Bind the Value property of a TableView column to the NSArrayController, controller key = arrangedObjects, Model Key Path is empty (because you're viewing the NSNumber instance itself, and not a property of NSNumber).
Bind the Content Array property of NSArrayController to your model (the NSMutableArray of NSNumbers). This is probably a property on your view controller or app delegate.
That's about it. You can also hook up buttons to the add: and remove: actions on the NSArrayController, and you'll be able to add and remove items from your array.
Also, you need to send a KVO notification whenever your NSMutableArray changes. For example, say your NSMutableArray is exposed through a property called "numbers":
[self willChangeValueForKey:#"numbers"];
[_numbers addObject:[NSNumber numberWithInt:123]];
[self didChangeValueForKey:#"numbers"];
You get these notifications for free if you set the "numbers" property to a new value:
self.numbers = [NSMutableArray arrayWithObject:foo];
I currently have a NSArrayController whose content property is (programmatically) set to an NSMutableDictionary and my UI has a single NSTableView. The information that the NSMutableDictionary contains is not set via the UI.
How would I use Cocoa bindings to display the dictionary keys in NSTableView? I already know how to use the DataSource methods, I just want to know how to use bindings for this.
I don't think it makes sense to set an array controller's content to an NSMutableDictionary. Rather, you should bind the array controller to the dictionary's allKeys property. Or consider using an NSDictionaryController, which was designed specifically for this purpose.