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You can populate a table view with full CRUD without writing any code.

Ok, no/not much code, but you need to set up quite a few things with Xcode interface builder. It ain’t easy to navigate in Xcode, so here is a step by step guide.

Array Controller

  1. Add an Array Controller to the storyboard scene
  2. In Attributes inspector, set Mode to Entity Name and enter your entity model name
  3. Enable Prepares Content so that that the table will load content automatically
  4. In Bindings inspector, enable bind to for Managed Object Context and select your scene
  5. Set Model Key Path to self.context

In your view controller, you will need to init the context property. You can read this post on my modern Core Data stack.

class ExchangeRateViewController: NSViewController {

    @objc dynamic var context: NSManagedObjectContext!

    override func viewDidLoad() {
        super.viewDidLoad()
        self.context = ... // Your Core Data stack viewContext
    }

}

Table View (Cell Based)

Let’s configure for a simple case using Cell Based table view. We cover View Based table next, which is the modern way and allow you to use any kind of view in each cell. The Cell Based way is only good for simple text fields.

  1. In Attributes inspector, set Content Mode to Cell Based.
  2. Select a column to bind
  3. Under Bindings inspector, enable for Value and bind to Array Controller
  4. The Controller Key is arrangedObjects
  5. The Model Key Path is your entity model attribute name
  6. Repeat for all columns

Run, and you will be able to edit the fields!

Ok, here’s the caveat: if your attribute is a String type, it works perfectly. For other types, you need a value transformer. Read it in next section.

But before we go on to value transformer, let’s know how to configure for View Based table view.

Table View (View Based)

  1. In Attributes inspector, set Content Mode to View Based.
  2. In Bindings inspector, bind Content to Array Controller. The Controller Key should already be arrangedObjects.
  3. Select the actual view to bind eg. NSTextField, NSDatePicker etc
  4. In Bindings inspector, bind Value to Table Cell View
  5. Set the Model Key Path to objectValue.attributeName (your entity attribute name!)

The most tricky part is in step (3) – selecting the correct view.

In a View Based table, you have to bind the actual view. You must select the correct view, which is in this complex hierarchy NSTableColumn > NSTableCellView > The actual view eg. NSTextField > NSTextFieldCell.

Value Transformer

When using Cocoa Binding, the data type might need some massaging. Value Transformer is 1 one of the concept that transforming the type. There is also formatters, which is more for formatting as String for display.

The full binding flow is daunting.

Creating a value transformer includes subclassing ValueTransformer and overriding 3 methods, and then register it with a name (String). I will not go into the details.

Add & Remove

It is common to have gradient buttons (the + and - square buttons) below the table view to easily add row or delete selected rows.

  1. Add a Gradient Button
  2. Under Connections inspector, drag the action to Array Controller, and select add:
  3. Repeat the same for the delete button but select remove:

But if you want more controls over adding, you might want to write your own methods. In the example below, I add a new model with a default date to now.

@IBAction func add(_ sender: Any) {
    let newModel = arrayController.newObject() as AnyObject
    newModel.setValue(Date(), forKey: "date")
    arrayController.addObject(newModel as Any)
}

@IBAction func remove(_ sender: Any) {
    // Do certain stuff before removing all selected rows
    arrayController.remove(atArrangedObjectIndexes: arrayController.selectionIndexes)
}

For this to work, you also need to set up binding to the table view’s selections:

  1. Select the table view > Binding inspector > Selection Indexes > Bind to the Array Controller
  2. Set Controller Key to selectionIndexes

Sort & Filter

This binds Array Controller to your NSSortDescriptor:

  1. Select Array Controller > Bindings inspector > Sort Descriptors > Bind to the view controller
  2. Set Model Key Path to self.sorts
  3. In your view controller, add the instance var @objc dynamic var sorts: [NSSortDescriptor]!
  4. Init sorts with an array NSSortDescriptor in viewDidLoad

Filter is similar, binding to the Filter Predicate.

With that, the table view content will sort and filter accordingly.

To sort by the table column, you need to these additionally:

  1. Select Table View > Bindings inspector > Sort Descriptors > Bind to the view controller
  2. Set Model Key Path to self.sorts
  3. Select a table column > Bindings inspector > Value > Bind to Array Controller
  4. Set the model key path eg. “date”
  5. Make sure Creates Sort Descriptor is enabled

With that, you can now click on a header and sort it ascending/descending.

Selection

You will probably also need to bind table view’s selectionIndexes to the array controller. This is needed so that if user select one, or multiple rows, the array controller selectedObjects will be correct.

  1. Select Table View > Bindings inspector > Selection Indexes > Bind to the Array Controller
  2. Set Controller Key to selectionIndexes

To know (observe) the selected objects, you will need to set up observation.

In viewDidLoad, arrayController.addObserver(self, forKeyPath: "selectedObjects", options: .new, context: nil). Then observe.

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    guard let keyPath = keyPath else { return }
    switch keyPath {

    case "selectedObjects":
        // arrayController.selectedObjects has changed

    default: break
    }
}

Conclusion

If you have followed the steps so far, you should find using Xcode interface builder to set up binding is a pain.. I would rather code than set up so many fields. In time to come, it is easy to forget how certain things are wired up.

As such, the alternative is to take away binding and array controller. Instead, simply use Core Data’s NSFetchedResultsController together with the NSTableView via the regular delegate and datasource patterns.


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@samwize

¯\_(ツ)_/¯

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