创建扩展Swift 4时出错：使用未声明的类型'UIFont'

Question

我正在创建的扩展名UIFont，它给出了一个错误。我附上了它的屏幕截图。导入时此错误消失UIFont。

import Foundation

extension UIFont {    
    class func appRegularFont(with size:CGFloat) -> UIFont {
        return UIFont(name:"HelveticaNeue-Bold", size: size)!
    }

    class func appMediumFont(with size:CGFloat) -> UIFont {
        return UIFont(name:"HelveticaNeue-Bold", size: size)!
    }

    class func appBoldFont(with size:CGFloat) -> UIFont {
        return UIFont(name:"HelveticaNeue-Bold", size: size)!
    }
}

Answer 1

转到您的扩展文件并将其导入

导入UIKit