Swift4 JSONDecoderExpected可以解码Dictionary< String，Any>但是找到了一个数组 [英] Swift4 JSONDecoderExpected to decode Dictionary<String, Any> but found an array instead

问题描述

这是我的新手，但是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功能，如下面的代码所示，并且正在接收此错误. /p>

快捷代码:

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
 }
}

并且JSON响应字符串显示为:

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

任何帮助将不胜感激.

解决方案

在这里，JSON数据是Objects的Array.

更改

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:为了更好地理解，这是我的视频系列，介绍了Swift 4中的JSON解析

I'm pretty newbie with this, but I've been attempting to work out how JSONDecoder works for a login function that needs to retrieve data from a MySQL database, as shown in my code below and am receiving this error.

Swift Code:

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()
    }

Temporary Struct I have been attempting to use:

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
 }
}

And the JSON response string reads:

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

Any help would be massively appreciated.

解决方案

Here, JSON data is Array of Objects.

change

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

to

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

Example:

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)

Note: For better understanding, this is my video series about JSON parsing in swift 4

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