String NSFontAttributeName已更改为字符串

我正在尝试正确设置导航栏的样式，我需要将字体更改为helvetica neue，大小点为19。我曾经使用过这段代码，但我注意到现在不起作用：

navigationController?.navigationBar.titleTextAttributes = [NSFontAttributeName: UIFont(name: "HelveticaNeue-Light", size: 19)]

发生这种情况是因为NSFontAttributeName的类型已更改为String，我已尝试使用

navigationController?.navigationBar.titleTextAttributes = [NSFontAttributeName: "HelveticaNeue-Light, 19"]

---

但是编译器继续给我一个与字体中的点大小相关的错误，我如何修复它？

构造函数返回一个可选（

UIFont？

）你必须打开它才能使用。添加

如果您确定有有效的字体名称：

Swift 4.2:

navigationController?.navigationBar.titleTextAttributes = [NSAttributedString.Key.font: UIFont(name: "HelveticaNeue-Light", size: 19)!]

navigationController?.navigationBar.titleTextAttributes = [NSAttributedStringKey.font: UIFont(name: "HelveticaNeue-Light", size: 19)!]

navigationController?.navigationBar.titleTextAttributes = [NSFontAttributeName: UIFont(name: "HelveticaNeue-Light", size: 19)!]

Swift 4:

navigationController?.navigationBar.titleTextAttributes = [NSAttributedString.Key.font: UIFont(name: "HelveticaNeue-Light", size: 19)!]

navigationController?.navigationBar.titleTextAttributes = [NSAttributedStringKey.font: UIFont(name: "HelveticaNeue-Light", size: 19)!]

navigationController?.navigationBar.titleTextAttributes = [NSFontAttributeName: UIFont(name: "HelveticaNeue-Light", size: 19)!]

Swift 3:

navigationController?.navigationBar.titleTextAttributes = [NSAttributedString.Key.font: UIFont(name: "HelveticaNeue-Light", size: 19)!]

navigationController?.navigationBar.titleTextAttributes = [NSAttributedStringKey.font: UIFont(name: "HelveticaNeue-Light", size: 19)!]

navigationController?.navigationBar.titleTextAttributes = [NSFontAttributeName: UIFont(name: "HelveticaNeue-Light", size: 19)!]

注意：如果在代码中使用静态名称设置字体，则在验证使用的字体名称有效后，强制展开是安全的。如果您是从外部源（用户或服务器）获取字体名称，则需要使用可选绑定，例如
If let font=UIFont（…
或
guard let font=UIFont）（…
在使用前安全地展开字体。
如果不推荐使用Swift 4NSFontAttributeName，则可以使用NSAttributedStringKey值设置属性

if let fontStyle = UIFont(name: "HelveticaNeue-Light", size: 19) {
  navigationController?.navigationBar.titleTextAttributes = [NSAttributedStringKey.font: fontStyle]
}

使用Swift 4.2
NSAttributedStringKey
更改为
NSAttributedStringKey.Key

if let fontStyle = UIFont(name: "HelveticaNeue-Light", size: 19) {
  navigationController?.navigationBar.titleTextAttributes = [NSAttributedString.Key.font: fontStyle]
}

有关NSAttributedStringKey的更多选项，您可以访问此链接

在Swift 4.2中，NSAttributedStringKey已重命名为NSAttributedString.Key

if let fontStyle = UIFont(name: "HelveticaNeue-Light", size: 19) {
  navigationController?.navigationBar.titleTextAttributes = [NSAttributedString.Key.font: fontStyle]
}

谢谢！正是我想要的！