Swift4 JSONDecoder 期望解码 Dictionary<String, Any> 但找到了一个数组 [重复]

Question

我对此很陌生，但我一直在尝试弄清楚 JSONDecoder 如何用于需要从 MySQL 数据库检索数据的登录函数，如下面的代码所示，并且收到此错误。

Swift 代码：

func testParseJson(){

                var request = URLRequest(url: URL(string: "https://test.php")!)
        request.httpMethod = "POST"

        let postString = ("Email=test&Password=test")
        print(postString)
        request.httpBody = postString.data(using: .utf8)

        let task = URLSession.shared.dataTask(with: request) { data, response, error in
            guard let data = data else { return }
            do {
                var responseString = String(data: data, encoding: .utf8)!
                print("new response string \(responseString)")
                let decoder = JSONDecoder()
                let newData = try decoder.decode(User.self, from: data)
                print(newData.Email)
                print(newData.UserType)
            } catch let err {
                print("Err", err)
            }
            }.resume()
    }

我一直在尝试使用的临时结构：

struct User: Decodable {
 let U_ID: String
 let Email: String
 let Password: String
 let UserType: String

private enum CodingKeys: String, CodingKey {
    case U_ID
    case Email
    case Password
    case UserType
 }
}

JSON 响应字符串为：

[{"U_ID":"1",
"Email":"test",
"Password":"test",
"UserType":"Teacher"}]

任何帮助将不胜感激。

Answer 1

这里，JSON 数据是 Array 的 Objects。

改变

try decoder.decode(User.self, from: data)

到

try decoder.decode(Array<User>.self, from: data)

示例：

var users = [User]()

let data = """
[{"U_ID":"1","Email":"test","Password":"test","UserType":"Teacher"}]
""".data(using: .utf8)

do{
    users = try JSONDecoder().decode(Array<User>.self, from: data!)
}catch{
    print(error.localizedDescription)
}

print(users.first?.Email)

注意：为了更好的理解，这是我的video系列，关于swift 4中的JSON解析