MacOS Swift Bundle项目：同一Nib文件下拉框切换视图实现方法

Hey there! Since you're new to Swift and macOS development (and working without Storyboards), let's walk through exactly how to switch views dynamically when an NSPopUpButton changes its selection. This approach uses child view controllers to keep your code clean and follows macOS best practices.

1. Prepare View Controllers for Each Item #

First, create separate NSViewController subclasses for each view you want to display. For example:

• Item1ViewController.swift (with its own Nib file, e.g., Item1ViewController.nib)
• Item2ViewController.swift (with its corresponding Nib)

Set up constraints in each Nib so the view fits neatly into a container—this will make swapping seamless later.

2. Configure Your Main Nib #

In your main Nib file (e.g., MainView.nib):

• Add an NSPopUpButton and populate its menu items (you can do this via the Attributes Inspector or programmatically later)
• Add an empty NSView to act as a container for your dynamic views. Name it contentContainerView and link it to your main view controller as an IBOutlet.
• Link the NSPopUpButton to your main controller as an IBOutlet, then set its action to a method like popupSelectionChanged(_:).

3. Implement the Selection Change Logic #

In your main view controller class:

First, declare variables to hold your child view controllers (so you don't recreate them every time selection changes):

private var currentChildVC: NSViewController?
private let item1VC = Item1ViewController(nibName: "Item1ViewController", bundle: nil)
private let item2VC = Item2ViewController(nibName: "Item2ViewController", bundle: nil)

Next, implement the action method that triggers when the popup selection changes:

@IBAction func popupSelectionChanged(_ sender: NSPopUpButton) {
    // Remove the currently displayed child view and controller
    currentChildVC?.view.removeFromSuperview()
    currentChildVC?.removeFromParent()
    
    // Pick the right view controller based on the selected item
    let selectedVC: NSViewController
    switch sender.selectedItem?.title {
    case "Item 1":
        selectedVC = item1VC
    case "Item 2":
        selectedVC = item2VC
    default:
        selectedVC = item1VC // Fallback to a default view
    }
    
    // Add the new child view controller to the container
    addChild(selectedVC)
    selectedVC.view.frame = contentContainerView.bounds
    // Ensure the child view resizes with the container
    selectedVC.view.autoresizingMask = [.width, .height]
    contentContainerView.addSubview(selectedVC.view)
    
    currentChildVC = selectedVC
}

4. Set the Initial View #

Don't forget to show a default view when your main controller loads. Add this to viewDidLoad():

override func viewDidLoad() {
    super.viewDidLoad()
    // Show Item 1 by default (replace `popUpButton` with your IBOutlet name)
    popupSelectionChanged(popUpButton)
}

Bonus Tips #

• If you prefer Auto Layout over autoresizing masks, replace the frame and autoresizing lines with:

  selectedVC.view.translatesAutoresizingMaskIntoConstraints = false
  NSLayoutConstraint.activate([
      selectedVC.view.topAnchor.constraint(equalTo: contentContainerView.topAnchor),
      selectedVC.view.leadingAnchor.constraint(equalTo: contentContainerView.leadingAnchor),
      selectedVC.view.trailingAnchor.constraint(equalTo: contentContainerView.trailingAnchor),
      selectedVC.view.bottomAnchor.constraint(equalTo: contentContainerView.bottomAnchor)
  ])
  

• To populate the popup button programmatically, add this to viewDidLoad():

  popUpButton.addItem(withTitle: "Item 1")
  popUpButton.addItem(withTitle: "Item 2")
  

• Double-check that all your Nib files are included in your Bundle target (in Xcode's "Build Phases" > "Copy Bundle Resources") to avoid loading errors.

内容的提问来源于stack exchange，提问作者Mohit