未找到 NSNotification.Name.didBecomeActiveNotification

Question

我正在 Xcode 10.1 上使用 10.14 部署目标开发 macOS 应用程序。根据文档，应该有一个 NSNotification.Name.didBecomeActiveNotification，但构建失败并出现Type 'NSNotification.Name?' has no member 'didBecomeActiveNotification'错误。我导入了 Cocoa、AppKit 和 Foundation。这是相关的代码：

NotificationCenter.default.addObserver(forName: .didBecomeActiveNotification, object: nil, queue: nil) { notification in
    print("\(notification)")
}

问题是什么？

Answer 1

它现在是一个类属性 NSApplication

NotificationCenter.default.addObserver(forName: NSApplication.didBecomeActiveNotification, object: nil, queue: nil) { notification in