Swift で Optional 型のやつを文字列に埋め込んだときの出力を変える

Example.swift

let text: String = "nullable"
let num: Int? = nil

print("text: \(text) num: \(num)")

/* output
> text: nullable num:
*/

StringInterpolation.swift

extension String.StringInterpolation {
    
    mutating func appendInterpolation(_ value: CustomStringConvertible?) {
        
        guard let value = value else {
            return
        }
        
        appendLiteral(String(describing: value))
    }
}