swift4 - Swift 4转换错误-NSAttributedStringKey:任何

Question

我最近转换了我的应用程序，但不断收到错误消息

"Cannot convert value of type '[String : Any]' to expected argument type '[NSAttributedStringKey: Any]?'

barButtonItem.setTitleTextAttributes(attributes, for: .normal)
整个代码:

 class func getBarButtonItem(title:String) -> UIBarButtonItem {
    let barButtonItem = UIBarButtonItem.init(title: title, style: .plain, target: nil, action: nil)
    let attributes = [NSAttributedStringKey.font.rawValue:  UIFont(name: "Helvetica-Bold", size: 15.0)!, NSAttributedStringKey.foregroundColor: UIColor.white] as! [String : Any]
    barButtonItem.setTitleTextAttributes(attributes, for: .normal)

    return barButtonItem
}

Answer 1

为什么会出现此错误
以前，您的attributes定义为[String: Any]，其中键来自Swt 4.2中的NSAttributedStringKey作为字符串或NSAttributedString.Key在迁移期间，编译器将尝试保留[String: Any]类型。但是，NSAttributedStringKey在swift 4中成为一个结构。因此，编译器尝试通过获取其原始值将其更改为字符串。
在这种情况下，setTitleTextAttributes正在寻找[NSAttributedStringKey: Any]，但您提供了[String: Any]要解决此错误:
删除.rawValue并将您的attributes转换为[NSAttributedStringKey: Any]即，更改以下行

let attributes = [NSAttributedStringKey.font.rawValue:
    UIFont(name: "Helvetica-Bold", size: 15.0)!, 
    NSAttributedStringKey.foregroundColor: UIColor.white] as! [String : Any]

至

let attributes = [NSAttributedStringKey.font:
    UIFont(name: "Helvetica-Bold", size: 15.0)!, 
    NSAttributedStringKey.foregroundColor: UIColor.white] as! [NSAttributedStringKey: Any]

在Swift 4.2中

 let attributes = [NSAttributedString.Key.font:
    UIFont(name: "Helvetica-Bold", size: 15.0)!, 
    NSAttributedString.Key.foregroundColor: UIColor.white] as! [NSAttributedStringKey: Any]