无法将[anyhashable：any]类型的值转换为[string：any]

Question

 let darkGray = UIColor.darkGray
    let lightGray = UIColor.lightGray
    let white = UIColor.white
    // Navigation bar background.
    UINavigationBar.appearance().barTintColor = darkGray
    UINavigationBar.appearance().tintColor = lightGray
    // Color of typed text in the search bar.
    let searchBarTextAttributes: [AnyHashable: Any] = [NSForegroundColorAttributeName: lightGray, NSFontAttributeName: UIFont.systemFont(ofSize: CGFloat(UIFont.systemFontSize))]
    UITextField.appearance(whenContainedInInstancesOf: [UISearchBar.self]).defaultTextAttributes = searchBarTextAttributes as! [String : Any]
    // Color of the placeholder text in the search bar prior to text entry.
    let placeholderAttributes: [AnyHashable: Any] = [NSForegroundColorAttributeName: white, NSFontAttributeName: UIFont.systemFont(ofSize: CGFloat(UIFont.systemFontSize))]
    // Color of the default search text.
    // NOTE: In a production scenario, "Search" would be a localized string.
    let attributedPlaceholder = NSAttributedString( string: "Search", attributes: placeholderAttributes)
    UITextField.appearance(whenContainedInInstancesOf: [UISearchBar.self]).attributedPlaceholder = attributedPlaceholder

在let attributionPlaceholder中，我想出了一个错误，想知道是否有人可以为我揭示这一点？

Answer 1

let placeholderAttributes: [AnyHashable: Any] = [NSForegroundColorAttributeName: UIColor.white, NSFontAttributeName: UIFont.systemFont(ofSize: CGFloat(UIFont.systemFontSize))]
    // Color of the default search text.
    // NOTE: In a production scenario, "Search" would be a localized string.
    let attributedPlaceholder = NSAttributedString( string: "Lookup", attributes: placeholderAttributes as? [String: Any])

这对我有用，谢谢。

Answer 2

可以用以下代码替换您的代码：

let placeholderAttributes = ["NSForegroundColorAttributeName": UIColor.white, "NSFontAttributeName": UIFont.systemFont(ofSize: CGFloat(UIFont.systemFontSize))]
// equivalent of: let placeholderAttributes: [String: Any?] = ...
let attributedPlaceholder = NSAttributedString( string: "Search", attributes: placeholderAttributes)

因为在这种情况下，您无法将AnyHashable转换为String，或[AnyHashable:Any?]转换为[String:Any?]。