在Swift 3中追加函数范围之外的变量

I am trying to append jsonFile, however, I am not able to append jsonFile with a new NSString unless I use a mutuable variable for the parameter file in the function. I have found the solution of using "inout" but in this case I get the error of "scaping closures can only capture inout parameters explicitly by value file.append(jsonData)I am trying to append jsonFile, however, I am n