How to create JSON from a dictionary in Swift 4?

问题

Edit: I have read the other answers on SO for the same issue , however Im unable to get the desired output. I have tried many variations as suggested in other questions but its not working.

I have a JSON snipped which needs to be added as the body when I open a websocket.

  sender: "system1@example.com",
  recipients:"system2@example.com",
  data: {
  text: "Test Message"
   },

So using Swift I did the following,

    var messageDictionary : [String: Any] = [
        "sender": "system1@example.com",
        "recipients":"system2@example.com",
        "data": [
        "text": "Test Message"
        ],
    ]
    do {
        let jsonData = try JSONSerialization.data(withJSONObject: messageDictionary, options: .prettyPrinted)
        let jsonString = String(data: jsonData, encoding: String.Encoding.ascii)
        socket.write(string: jsonString!)
        print(jsonString)
    } catch {
        print(error.localizedDescription)
    }

When I print the jsonString, I get

    Optional("{\n  \"sender\" : \"system1@example.com\",\n  \"data\" : {\n    
    \"text\" : \"Test Message\"\n  },\n  \"recipients\" : 
    \"system2@example.com\"\n}")

as the console output. I expected the above snippet to be formatted as JSON. How to get the output as normal JSON without the /n and additional spaces? Im using Swift 4 and Xcode 9.1

Edit 2:

   let jsonData = try JSONSerialization.data(withJSONObject: messageDictionary, options: [])
   let decoded = try JSONSerialization.jsonObject(with: jsonData, options: [])

I tried doing the above and I get the following as the output:

    {
        data =     {
            text = Test Message;
    };
        recipients = "system1@example.com";
        sender = "system2@example.com";
    }

However the websocket expects this:

    { "sender":"system1@example.com","recipients":
    ["system2@example.com"],"data":{"text":"Test Message"}}

Even with a slight variation like misplacing of double quotes the websocket server doesnt accept the input. How to exactly format the JSOn this way so that the websocket can accept it?

回答1:

After trying out various ways the below way is what worked for me for getting the exact format required by the backend.

    var messageDictionary = [
        "sender":"system1@example.com",
        "recipients":["system2@example.com"],
        "data":[
            "text" : data
        ]
        ] as [String : Any]

        let jsonData = try! JSONSerialization.data(withJSONObject: messageDictionary)
        let jsonString = NSString(data: jsonData, encoding: String.Encoding.utf8.rawValue)

回答2:

Additionally, you can just cast to String

let jsonData = try? JSONSerialization.data(withJSONObject: dict, options: .prettyPrinted)
let jsonString = String(data: jsonData!, encoding: .utf8)

来源：https://stackoverflow.com/questions/47524218/how-to-create-json-from-a-dictionary-in-swift-4

标签

json

swift

nsdictionary