覆盖NSTreeController的rangedObjects

Question

In my project an NSTreeController is bound to an NSOutlineView (cocoa binding). For some reason I can't use NSPredicate to filter data from Core Data. So I tried to override arrangedObjects of NSTreeController , but the overriding arrangedObjects has not even been fired . (I set a debugging breakpoint inside it.) The code compiles well and I've already changed the instance to my CleanTreeController . I only found an unanswered question asked a decade ago in the mailing list.

// Subclass of NSTreeController
class CleanTreeController: NSTreeController {
    init() {
        // This gets called.
        super.init(content: nil)
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
    }

    override var arrangedObjects: Any {
        let oldArranged = super.arrangedObjects

        let selector = NSSelectorFromString("childNodes")

        guard let oldChildren = (oldArranged as! NSObject)
                            .perform(selector).takeUnretainedValue() as? [NSTreeNode]
        else
        {
            return oldArranged
        }

        let children = oldChildren.filter { (treeNode) in
            //... do some filtering
        }

        return TreeNodeProxy(with: children)
    }
}

// Homemade NSTreeNodeProxy
class TreeNodeProxy : NSObject {

    fileprivate var rootNode : NSTreeNode

    init(with children : [NSTreeNode]) {
        self.rootNode = NSTreeNode()
        self.rootNode.mutableChildren.addObjects(from: children)
    }

    @objc(childNodes)
    var children: [NSTreeNode]? {
        return rootNode.children
    }

    @objc(descendantNodeAtIndexPath:)
    func descendant(at indexPath: IndexPath) -> NSTreeNode? {
        return rootNode.descendant(at: indexPath)
    }
}

I've found

The value returned by NSTreeController's arrangedObjects method is opaque. You should only observe this property to determine that a change has occurred.

in the doc . So how can NSOutineView consume arrangedObjects without reading it (directly)?

Answer 1

设置fetchPredicate的的NSTreeController在厦门国际银行或代码。