如果没有更多的上下文swift 4.0,表达式的类型是不明确的

Question

我正在实现pod'Socket.IO-Client-Swift '

但在SocketEngine.swift文件中我收到此错误.

 private func handleBase64(message: String) {
            // binary in base64 string
            let noPrefix = message[message.index(message.startIndex, offsetBy: 2)..<message.endIndex]

            if let data = Data(base64Encoded: noPrefix, options: .ignoreUnknownCharacters) {
                client?.parseEngineBinaryData(data)
            }
        }

提前致谢!!

Answer 1

noPrefix是类型Substring,只是强制它到字符串:

if let data: Data = Data(base64Encoded: String(noPrefix), options: .ignoreUnknownCharacters) {
    ...
}