Autosave Expanded Items of NSOutlineView doesn't work

Question

I am trying to use the "Autosave Expanded Items" feature. When I expand a group with its children and restart the application all children are collapsed again and I don't know why they won't stay expanded. I'm using core data to store my source list items.

This is what I have done/set so far:

• Checked "Autosave Expanded Items" in NSOutlineView (Source List)
• Set a name for "Autosave"
• dataSource and delegate outlets assigned to my controller

This is my implementation for outlineView:persistentObjectForItem and outlineView:itemForPersistentObject.

- (id)outlineView:(NSOutlineView *)anOutlineView itemForPersistentObject:(id)object
{
    NSURL *objectURI = [[NSURL alloc] initWithString:(NSString *)object];  
    NSManagedObjectID *mObjectID = [_persistentStoreCoordinator managedObjectIDForURIRepresentation:objectURI]; 
    NSManagedObject *item = [_managedObjectContext existingObjectWithID:mObjectID error:nil];
    return item;  
}

- (id)outlineView:(NSOutlineView *)anOutlineView persistentObjectForItem:(id)item
{
    NSManagedObject *object = [item representedObject];
    NSManagedObjectID *objectID = [object objectID];
    return [[objectID URIRepresentation] absoluteString];
}

Any ideas? Thanks.

EDIT: I have a clue! The problem is maybe that the tree controller has not prepared its content on time. The methods applicationDidFinishLaunching, outlineView:persistentObjectForItem etc. are being be executed before the data has loaded or rather the NSOutlineView hasn't finished initializing yet. Any ideas how to solve this?

Answer 1

I've had the problem that my implementation of -outlineView:itemForPersistentObject: was not called at all. It turns out that this method is called when either "autosaveExpandedItems" or "autosaveName" is set. My solution was to set both properties in Code and NOT in InterfaceBuilder. When i set the properties after the delegate is assigned, the method gets called.

Answer 2

I got this to work - you need to return the corresponding tree node instead of "just" its represented object.

In itemForPersistentObject:, instead of return item; you need return [self itemForObject:item inNodes:[_treeController.arrangedObjects childNodes]];

with

- (id)itemForObject:(id)object inNodes:(NSArray *)nodes {
    for (NSTreeNode *node in nodes) {
        if ([node representedObject] == object)
            return node;

        id item = [self itemForObject:object inNodes:node.childNodes];
        if (item)
            return item;
    }

    return nil;
}

where _treeController is the NSTreeController instance that you use to populate the outline view.

Answer 3

Expanding on Karsten's solution:

The method -outlineView:itemForPersistentObject: gets called after doing what Karsten suggests, but ONLY if you also set the datasource before setting the delegate.

So if Karsten's answer doesn't seem to work, check where your datasource is set and adjust accordingly.

(wanted to write this as a comment but I'm not allowed due to my newbie status ...)

Answer 4

Swift 5 answer

Karsten is right, itemForPersistentObject must return a NSTreeNode.

Here is a Swift 5 version of the solution:

// This method should return a NSTreeNode object
func outlineView(_ outlineView: NSOutlineView, itemForPersistentObject object: Any) -> Any? {
    guard let uriAsString = object as? String,
    let uri = URL(string: uriAsString) else { return nil }

    if let psc = self.managedObjectContext.persistentStoreCoordinator,
        let moID = psc.managedObjectID(forURIRepresentation: uri),
        let group = self.managedObjectContext.object(with: moID) as? MyGroupEntity,
        let nodes = self.expensesTreeController.arrangedObjects.children {
        return self.findNode(for: group, in: nodes)
    }
    return nil
}

/// Utility method to find the corresponding NSTreeNode for a given represented object
private func findNode(for object: NSManagedObject, in nodes: [NSTreeNode]) -> NSTreeNode? {
    for treeNode in nodes {
        if (treeNode.representedObject as? NSManagedObject) === object {
            return treeNode
        }
    }
    return nil
}

Answer 5

I never got this working.

This is my current way of doing it:

First, I added an attribute "isExpanded" and saved for each node the status in the database.

Second, I expand the nodes when my treeController has prepared its content.

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{  
    [treeSectionController addObserver:self
                     forKeyPath:@"content"
                        options:0
                        context:nil]; 
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object     change:(NSDictionary *)change context:(void *)context
{
    if (object == treeSectionController) {
        NSArray *sectionArray = [[treeSectionController arrangedObjects]     childNodes];
        for (NSTreeNode *node in sectionArray) {
             if([[node representedObject] isExpandedValue]) {
                 [outlinePilesView expandItem:node];
             }
        }
        [treeSectionController removeObserver:self forKeyPath:@"content"];
    }
}

Answer 6

Wow! 6 years later and this is still causing headaches.

I couldn't get this working initially, even with Karsten's helpful solution re setting autoSaveName & autosaveExpandedItems in code; itemForPersistentObject was still being called before the outlineView was populated. The solution for me, whilst not very elegant, was to set a delay of .5 seconds before setting autosaveExpandedItems & autoSaveName. The half second delay in my app is not noticeable. I used Vomi's code as well. Delegate and dataSource are set in IB bindings. Here's full solution:

override func viewDidLoad() {
    super.viewDidLoad()

    let _ = Timer.scheduledTimer(withTimeInterval: 0.5, repeats: false) { (timer) in
        self.keywordsOutlineView.autosaveExpandedItems = true
        self.keywordsOutlineView.autosaveName = "KeywordsOutlineView"
        timer.invalidate()
    }

}

func outlineView(_ outlineView: NSOutlineView, persistentObjectForItem item: Any?) -> Any? {
    
    if let node = item as? NSTreeNode {
        if let object = node.representedObject as? FTKeyword {
            return object.objectID.uriRepresentation().absoluteString
        }
    }
    return nil
}

// This method should return a NSTreeNode object
func outlineView(_ outlineView: NSOutlineView, itemForPersistentObject object: Any) -> Any? {
    
    if outlineView == keywordsOutlineView {
        
        guard let uriAsString = object as? String,
            let uri = URL(string: uriAsString) else { return nil }
        
            if let psc = self.managedObjectContext.persistentStoreCoordinator,
                let moID = psc.managedObjectID(forURIRepresentation: uri),
                let group = self.managedObjectContext.object(with: moID) as? FTKeyword,
                let nodes = self.keywordsTreeController.arrangedObjects.children {
                
                return self.findNode(for: group, in: nodes)
            }
            return nil
        

    }
    return nil
}

/// Utility method to find the corresponding NSTreeNode for a given represented object
private func findNode(for object: NSManagedObject, in nodes: [NSTreeNode]) -> NSTreeNode? {
    
    for treeNode in nodes {
        if (treeNode.representedObject as? NSManagedObject) === object {
            return treeNode
        }
    }
    return nil
}