用代码将NSTreeController绑定到NSOutlineView

Question

I'm looking to bind an NSTreeController , which in turn is bound to an array, to an NSOutlineView :

treeController.bind(NSContentArrayBinding,
    toObject: viewModel,
    withKeyPath: "items",
    options: nil)

outlineView.bind(NSContentBinding,
    toObject: treeController,
    withKeyPath: "arrangedObjects",
    options: nil)

outlineView.bind(NSSortDescriptorsBinding,
    toObject: treeController,
    withKeyPath: "sortDescriptors",
    options: nil)

outlineView.bind(NSSortDescriptorsBinding,
    toObject: treeController,
    withKeyPath: "selectionIndexPaths",
    options: nil)

items in viewModel contains an object which in turn has its own array of children.

However, when doing the above binding, nothing shows in the UI. I've also tried adding a column:

let column = NSTableColumn(identifier: "0")

column.bind(NSValueBinding,
    toObject: treeController,
    withKeyPath: "arrangedObjects.displayName"),
    options: nil)

outlineView.addTableColumn(column)

But to no avail, I still don't get any results rendered in the UI.

What am I missing to make the binding work? The NSOutlineView renders as expected, just with no items in.

(Feel free to answer in Objective-C, I'm not picky on language choice)

Answer 1

You need to set the childrenKeyPath of the tree controller. Otherwise, the tree controller can't understand the data structure that it's pointed to. The childrenKeyPath should be the key path, relative to an element of the items array, that gives an array of that element's children.