// 非泛型函数，查找指定字符串在数组中的索引 func findIndex(ofString valueToFind: String, in array: [String]) -> Int? { for (index, value) in array.enumerated() { if value == valueToFind { // 找到返回索引值 return index } } return nil } let strings = ["google", "weibo", "taobao", "W3xue", "facebook"] if let foundIndex = findIndex(ofString: "W3xue", in: strings) { print("W3xue 的索引为 \(foundIndex)") }