swift - 修复 navFont 不能用于类型 '...' 的实例？

Question

我在使用 navFont 时遇到了一些问题。 在我的文件 CustomAppearance.swift 中，出现错误

navFont can't be used on instance of type 'Custom Appearance'.

这是我的代码:

import Foundation

struct CustomAppearance {

   static let navFont = UIFont(name: "SF-UI-Text-Light", size: 17.0)

   func applyCustomAppearanceToNavigationBar() {
       UINavigationBar.appearance().translucent = false
       UINavigationBar.appearance().barTintColor = UIColor.whiteColor()
       UINavigationBar.appearance().tintColor = UIColor.blackColor()
       UINavigationBar.appearance().titleTextAttributes = [NSFontAttributeName: navFont!, NSForegroundColorAttributeName: UIColor.blackColor() ]
   }
}

Answer 1

您必须为静态变量使用限定名称:

struct CustomAppearance {

    static let navFont = UIFont(name: "SF-UI-Text-Light", size: 17.0)

    func applyCustomAppearanceToNavigationBar() {
        UINavigationBar.appearance().titleTextAttributes = [
            NSFontAttributeName: CustomAppearance.navFont!,
            NSForegroundColorAttributeName: UIColor.blackColor()
        ]
    }
}

在 Swift 的 future 版本中，语法 Self.navFont! 也将成为可能(参见 Swift Evolution - Universal Self )