我正在关注Apple'sDocs在Swift中使用Xcode6-Beta6创建PDF文件varcurrentText:CFAttributedStringRef=CFAttributedStringCreate(nil,textView.textasNSString,nil)if(currentText){//编译器抛出Type'CFAttributedStringRef'doesnotconformtoprotocol'BooleanType'错误如果我使用if(currentText!=nil)我会得到'CFAttributedStringRef'isnotconvertiblet