如何使用NSTreeController正确显示枚举对象

Question

我正在尝试了解如何使用NSTreeController。当我添加一个方法（下面提供了SourceView示例的类和方法的段）来迭代目录的内容，该目录通过NSTreeController传输到NSOutlineView。但是，NSOutlineView只显示第一个对象（根对象）（您可以在下面的方案中看到它）。

类NSTreeController方法：

- (void)performAddChild:(TreeAdditionObj *)treeAddition {
    if ([[treeController selectedObjects] count] > 0) {
        // we have a selection
        if ([[[treeController selectedObjects] objectAtIndex:0] isLeaf]) {
            // trying to add a child to a selected leaf node, so select its parent for add
            [self selectParentFromSelection];
        }
    }

    // find the selection to insert our node
    NSIndexPath *indexPath;
    if ([[treeController selectedObjects] count] > 0) {
        // we have a selection, insert at the end of the selection
        indexPath = [treeController selectionIndexPath];
        indexPath = [indexPath indexPathByAddingIndex:[[[[treeController selectedObjects] objectAtIndex:0] children] count]];
    } else {
        // no selection, just add the child to the end of the tree
        indexPath = [NSIndexPath indexPathWithIndex:[contents count]];
    }

    // create a leaf node
    BaseNode *node = [[BaseNode alloc] initLeaf];
    node.urlString = [treeAddition nodeURL];

    if ([treeAddition nodeURL]) {
        if ([[treeAddition nodeURL] length] > 0) {
            // the child to insert has a valid URL, use its display name as the node title
            if ([treeAddition nodeName])
                node.nodeTitle = [treeAddition nodeName];
            else
                node.nodeTitle = [[NSFileManager defaultManager] displayNameAtPath:[node urlString]];
        }
    }

    // the user is adding a child node, tell the controller directly
    [treeController insertObject:node atArrangedObjectIndexPath:indexPath];

    // adding a child automatically becomes selected by NSOutlineView, so keep its parent selected
    if ([treeAddition selectItsParent])
        [self selectParentFromSelection];
}

- (void)addChild:(NSString *)url withName:(NSString *)nameStr selectParent:(BOOL)select {
    TreeAdditionObj *treeObjInfo = [[TreeAdditionObj alloc] initWithURL:url
                                                               withName:nameStr
                                                        selectItsParent:select];

    if (buildingOutlineView) {
        // add the child node to the tree controller, but on the main thread to avoid lock ups
        [self performSelectorOnMainThread:@selector(performAddChild:)
                               withObject:treeObjInfo
                            waitUntilDone:YES];
    } else {
        [self performAddChild:treeObjInfo];
    }
}

显示目录的枚举对象的方法：

- (void)addFinderSection {
    [self addFolder:@"FINDER FILES"];
    NSError *error = nil;
    NSEnumerator *urls = [[[NSFileManager defaultManager] contentsOfDirectoryAtURL:self.url includingPropertiesForKeys:[NSArray arrayWithObjects: nil] options:(NSDirectoryEnumerationSkipsHiddenFiles) error:&error] objectEnumerator];

    for (NSURL *url in urls) {
    BOOL isDirectory;
    if ([[NSFileManager defaultManager] fileExistsAtPath:[url path] isDirectory:&isDirectory]) {
        if (isDirectory) {
            if (![[NSWorkspace sharedWorkspace] isFilePackageAtPath:[url path]]) {
                NSLog(@"IS DIRECTORY %@", url);
                [self addChild:[url path] withName:NO selectParent:YES];
            }
        } else {
            NSLog(@"IS FIlE %@", url);
            [self addChild:[url path] withName:NO selectParent:YES];
        }
    }
}
    [self selectParentFromSelection];
}

我的错误可能就是NSTreeController没有区分简单对象（文件）和目录（文件夹）。

但是，当我在没有NSTreeController的情况下填写NSOutlineView时，所有内容都显示正确：

注意：如果使用方法addFolder :(在SourceView示例中，它用于创建其他对象的父组），则每个下一个对象都显示为上一个子组。

您能帮我正确显示这些方法中的文件夹内容吗？