ios - 将 CATextLayer 字体转换为 UIFont

Question

CATextLayer.font 属性是一个不透明的 CFTypeRef。有没有办法将该引用转换为 UIFont？我不介意它是否返回可选的 UIFont。

Answer 1

我刚刚编写了以下应该处理的扩展:CTFont、CGFont、字符串名称或 UIFont:

extension CATextLayer {
    public var typeFace:UIFont? {
        let name:String
        switch font {
        case let ctFont as CTFont :
            // If you assign a UIFont to CATextLayer.font
            // it is implicitly converted to CTFont,
            // so this case will be called.
            guard let _name = CTFontCopyName(ctFont, kCTFontPostScriptNameKey) else {
                return nil
            }
            name = _name as NSString as String
        case let cgFont as CGFont :
            guard let _name = cgFont.postScriptName else {
                return nil
            }
            name = _name as NSString as String
        case let string as NSString :
            name = string as String
        case let string as String :
            name = string
        default:
            return nil
        }
        return UIFont(name:name, size:fontSize)
    }
}

附带说明一下，我发现文档中的这条评论不准确:

In iOS, you cannot assign a UIFont object to this property.

根据我的测试，我能够在 CATextLayer.font 上设置一个 UIFont，它似乎工作正常。

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编辑

事实证明，当您将 UIFont 分配给 CATextLayer.font 时，它会在幕后转换为 CTFont，因此为了返回 UIFont 有必要将 CTFont 转换为 UIFont(我的代码就是这样做的)。简单地转换为 UIFont 是行不通的。