Issue with networking and Codable class

Question

Created Jan ’21

Replies 9

Boosts 0

Views 1.1k

Participants 2

Hello,
I’m having a little issue with my Codable class…
I have an Int which I will Post on my API. But when I GET back, it is a String.
Let me show you some code:

this is my class:

Code Block Swiftclass NFCDataSec: ObservableObject, Codable {
    enum CodingKeys: String, CodingKey {
        case firstName, lastName, age
    }
    @Published var lastName: String = ""
    @Published var firstName: String = ""
    @Published var age: Int = 0
    init() {    }
    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        lastName = try container.decode(String.self, forKey: .lastName)
        firstName = try container.decode(String.self, forKey: .firstName)
        age = try container.decode(Int.self, forKey: .age) /* (1) */
    }
    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(firstName, forKey: .firstName)
        try container.encode(lastName, forKey: .lastName)
        try container.encode(age, forKey: .age)
    }
}

this is my JSON Post request:

Code Block Swift        func SecuringData() throws {
            guard let encoded = try? JSONEncoder().encode(dataToWrite) else {
                print("Fail to encode SecuringData - NFCDataSec")
                return
            }
            let url = URL(string: "https://MY_API.COM/api/sendToChip")!
            var request = URLRequest(url: url)
            request.setValue("application/json", forHTTPHeaderField: "Content-Type")
            request.httpMethod = "POST"
            request.httpBody = encoded
            URLSession.shared.dataTask(with: request) { data, res, error in
                guard let httpResponse = res as? HTTPURLResponse,
                        (200...299).contains(httpResponse.statusCode) else {
                        self.handleServerError(res)
                    return
                }
                if let data = data {
                    let decoder = JSONDecoder()
                    if let json = try? decoder.decode(NFCDataSec.self, from: data) {
                        print(json)
                    }
                    else {
                        let dataString = String(decoding: data, as: UTF8.self)
                        print("Invalid response \(dataString)") /* (2) */
                    }
                }
            }.resume()

(1) the API GET returns String instead of Int - but it needs to have Int when I’m making the POSTmethod
(2) I get an invalid response from the API when I GET the data back from it.

Here is an exemple of working JSON

POST:

Code Block {
	"lastName":"John",
	"firstName":"Taylor",
	"age":23
}

GET:

Code Block {
    "firstName": "8ac18f61",
    "lastName": "88cf8f64dc719eac6a",
    "age": "e893"
}

Answered by Paul_a_Dance in 656203022

If you expect dataToWrite to be updated, you need to explicitly update it in the completion handler of dataTask.

If I understand correctly and to be sure, I need to to it in this part of the function, where I check the server's response ?

Code Block Swiftif let data = data {
    let decoder = JSONDecoder()
    print("this is what i'm retreiving from the API \(String(decoding: data, as: UTF8.self))")
    if let json = try? decoder.decode(NFCDataSec.self, from: data) {
        print(json)
        print(self.dataToWrite.firstName)
    }
}

And I need to do like so ?

Code Block Swift    if let json = try? decoder.decode(NFCDataSec.self, from: data) {
        print(json)
        self.dataToWrite.firstName = json.firstName
    }

Boost

Answer 1

OOPer OP

Jan ’21

It depends on what the API does, but, if the API returns String, you may need to prepare a type accepting String.

Add another struct to receive the value from the API:

Code Block struct NFCDataSecAPI: Codable {
    var lastName: String = ""
    var firstName: String = ""
    var age: String = "0"
}

Or use only this one and change other parts of your code.

0

Answer 2

Paul_a_Dance OP

Jan ’21

I created a new variable @Published var stringAge: String = "" and edited my decoder with this new variable, and it is fixed.

Code Block Swiftrequired init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        lastName = try container.decode(String.self, forKey: .lastName)
        firstName = try container.decode(String.self, forKey: .firstName)
/*      age = try container.decode(Int.self, forKey: .age) */
        stringAge = try container.decode(String.self, forKey: .age)
}

Here is a piece of mu function:

Code Block Swiftif let data = data {
                    let decoder = JSONDecoder()
                    print("this is what i'm retreiving from the API \(String(decoding: data, as: UTF8.self))")
                    if let json = try? decoder.decode(NFCDataSec.self, from: data) {
                        print(json) /* (1) */
                        print(self.dataToWrite.firstName) /* (2) */
                    }

Here is my console log:

Code Block JSONEncoded data: 
		{"lastName":"John","firstName":"Paul","age":23}
this is what i'm retreiving from the API 
		{"firstName":"504ae2d3","lastName":"5244e2d626d03a7e8f","age":"3218"}
Healthsafe.NFCDataSec  /* (1) */
Paul /* (2) */

I can't understand, now, why my class is not updated with the retrieved data (2).

0

Answer 3

OOPer OP

Jan ’21

Could it be because I'm not using the main thread to POSTand GET from the API ?

I do not think so. You code is disposing the most important error info, so nothing sure.

(UPDATE)
Seems you have updated your last post.

I can't understand, now, why my class is not updated with the retrieved data (2).

Where is the code updating your class?

0

Answer 4

Paul_a_Dance OP

Jan ’21

Seems you have updated your last post.

Yes sorry, I updated it because I forgot to change a type and it worked just after posting the first version. I forgot to tell it was updated.

Where is the code updating your class?

I thought by doing this line it would automatically update my class with the resent values

Code Block  Swift		if let json = try? decoder.decode(NFCDataSec.self, from: data)

0

Answer 5

OOPer OP

Jan ’21

I thought by doing this line it would automatically update my class with the resent values

As a fact you can see, it does not.

If you expect dataToWrite to be updated, you need to explicitly update it in the completion handler of dataTask.

0

Answer 6

Paul_a_Dance OP

Jan ’21

Accepted Answer

If you expect dataToWrite to be updated, you need to explicitly update it in the completion handler of dataTask.

If I understand correctly and to be sure, I need to to it in this part of the function, where I check the server's response ?

Code Block Swiftif let data = data {
    let decoder = JSONDecoder()
    print("this is what i'm retreiving from the API \(String(decoding: data, as: UTF8.self))")
    if let json = try? decoder.decode(NFCDataSec.self, from: data) {
        print(json)
        print(self.dataToWrite.firstName)
    }
}

And I need to do like so ?

Code Block Swift    if let json = try? decoder.decode(NFCDataSec.self, from: data) {
        print(json)
        self.dataToWrite.firstName = json.firstName
    }

0

Answer 7

OOPer OP

Jan ’21

And I need to do like so ?

Nearly, yes. Depends on the definition of dataToWrite.
(And I would never use try? in this case. Better use do-try-catch.)

0

Answer 8

Paul_a_Dance OP

Jan ’21

Nearly, yes. Depends on the definition of dataToWrite.
It works, the data are stored in the class.

I have a question a bit similar, but I can't figure out the issue.
Let me explain: I have a connection URL where I send my id and password and I'm supposed to GET id, sessionID and token but I always receive an invalid response (it is the same code as above). When I send the JSON with Postman I have no error ...

0

Answer 9

OOPer OP

Jan ’21

I have a question a bit similar, but I can't figure out the issue.

Ignoring a reply for 1 week and post another question???

...

You should start a new thread for your new question, better include a link to this thread.

0