预期返回字符串"的函数中缺少返回

Missing return in a function expected to return 'String'

应该函数 return 什么，因为你没有设置 return 如果不匹配任何一个 question.hasPrefix()

should the function return something , because you did not set return if do not match any one question.hasPrefix()

 func responseToQuestion(question: String) -> String {

            if question.hasPrefix("hello") {
                return "Hello"
            } else if question.hasPrefix("where") {
                return "There"
            } else if question.hasPrefix("what"){
                return "I don't know"
            }
          return "something"
        }