Implementing NSOutlineView with Pure Code in macOS: A Step‑by‑Step Guide

The article describes how to replace storyboard‑based NSOutlineView implementations with a pure‑code solution for macOS applications.

Step 1 – Initialize the outline view and its container. Create an NSTableColumn , configure its resizing mask, instantiate an NSOutlineView , enable column resizing, hide the header, set the column autoresizing style, and embed the outline view in an NSScrollView whose documentView is the outline view. Finally assign the scroll view to the view controller’s self.view .

NSTableColumn *tableColumn = [[NSTableColumn alloc] init];
 tableColumn.resizingMask = NSTableColumnAutoresizingMask;
 NSOutlineView *outlineView = [[NSOutlineView alloc] init];
 outlineView.allowsColumnResizing = YES;
 outlineView.headerView = nil;
 outlineView.columnAutoresizingStyle = NSTableViewFirstColumnOnlyAutoresizingStyle;
 outlineView.usesAlternatingRowBackgroundColors = YES;
 [outlineView addTableColumn:tableColumn];
 NSScrollView *scrollView = [[NSScrollView alloc] init];
 scrollView.documentView = outlineView;
 scrollView.hasVerticalScroller = YES;
 scrollView.autohidesScrollers = YES;
 self.view = scrollView;

Step 2 – Prepare the data model. Define a simple model class with NSString *name and NSArray *childNodes . Populate a hierarchy of these objects, ensuring each node’s children are of the same type.

Step 3 – Custom cell view. Subclass NSTableCellView (e.g., OutlineItemCellView ) and override -setObjectValue: to update UI elements such as self.textField.stringValue based on the model’s name .

Step 4 – Implement data source methods. Provide implementations for:

-outlineView:numberOfChildrenOfItem: – return child count.

-outlineView:child:ofItem: – return the appropriate child model.

-outlineView:isItemExpandable: – indicate expandability based on child count.

-outlineView:objectValueForTableColumn:byItem: – return the model object.

Step 5 – Implement delegate methods. Create views in -outlineView:viewForTableColumn:item: using makeViewWithIdentifier: or allocate a new OutlineItemCellView if nil, set its identifier, and return it. Optionally customize row appearance by overriding -outlineView:rowViewForItem: with a subclass of NSTableRowView .

Step 6 – Handle selection. Implement -outlineViewSelectionDidChange: to retrieve the selected item via selectedRow and itemAtRow: , then log or process the model’s name .

After completing these steps, the application displays a functional outline menu with expandable groups, custom cell styling, and proper selection handling, all built without Interface Builder.