nSarray包含两个元素，但MyArray [0]为零

Question

我正在尝试从文件加载笔尖。

我有此代码，从这里

protocol NibLoadable {
  static var nibName: String? { get }
  static func createFromNib(in bundle: Bundle) -> Self?
}
extension NibLoadable where Self: NSView {
  static var nibName: String? {
    return String(describing: Self.self)
  }
  static func createFromNib(in bundle: Bundle = Bundle.main) -> Self? {
    guard let nibName = nibName else { return nil }
    var topLevelArray: NSArray? = nil
    bundle.loadNibNamed(NSNib.Name(nibName), owner: self, topLevelObjects: &topLevelArray)
    guard let results = topLevelArray else { return nil }
//    let views = Array<Any>(results).filter { $0 is Self }
//    return views.last as? Self
    let element =      results[0] as? Self
    return results[0] as? Self
  }
}

结果有两个元素，一个nsview和nsapplication。

这里的问题是element是零。评论的代码也给了我nil。

我是Swift的新手。此Self传递或在createFromNib的最后一行中表示什么？

Answer 1

不能保证第一个对象是请求的视图。

使用first(where

获得正确的视图

并声明nibName不可接受为要求。

protocol NibLoadable {
    static var nibName: String { get }
    static func createFromNib(in bundle: Bundle) -> Self?
}
extension NibLoadable where Self: NSView {    
    static var nibName: String {
        return String(describing: Self.self)
    }
    static func createFromNib(in bundle: Bundle = Bundle.main) -> Self? {
        var topLevelArray: NSArray? // Optionals are nil by default
        bundle.loadNibNamed(NSNib.Name(nibName), owner: self, topLevelObjects: &topLevelArray)
        return topLevelArray?.first(where: { $0 is Self }) as? Self
    }
}

Answer 2

几个小时后尝试使用不存在的文档，我随之而来，更简单。

  func loadViewFromNib() {
    var topLevelArray : NSArray?
    let bundle = Bundle(for: type(of: self))
    let nib = NSNib(nibNamed: .init(String(describing: type(of: self))), bundle: bundle)!
    nib.instantiate(withOwner: self, topLevelObjects: &topLevelArray)
    let myView = topLevelArray?.first(where: { $0 is NSView }) as? NSView
    addSubview(myView!)
}

感谢@Vadian所做的所有努力。