在 Swift 中发布解码异步/等待响应

Question

I am trying to submit an order to production but keep getting a decoding error and I have no idea where it's going wrong.

This is the full error:

ERROR DECODING keyNotFound(CodingKeys(stringValue: "id", intValue: nil), Swift.DecodingError.Context(codingPath: [], debugDescription: "No value associated with key CodingKeys(stringValue: "id", intValue: nil) ("id").", underlyingError: nil))

My Model:

struct PrintifyOrderResponse: Codable {
    let id: String
}

My function/call:

func fetch<T: Codable>(type: PrintifyRequestType) async throws -> T? {
    let req = type.getRequest()
    
    let (data, _) = try await URLSession.shared.data(for: req)
    
    do {
        let decoder = JSONDecoder()
        let decoded = try decoder.decode(T.self, from: data)
        return decoded
    } catch {
        print("ERROR DECODING")
        print(error)
        print()
        print(error.localizedDescription)
        return nil
    }
}

in async func:

do {
        var res: PrintifyOrderResponse?
        res = try await service.fetch(type: .sendToProduction(id))
        guard let res = res else {
            statusError(message: "Error sending to production")
            return
        }
        
        orderSuccess(id: res.id)
        
    } catch {
        print("ERROR: \(error)")
        statusError()
    }
}

The response is quite simple as seen from postman below. I'm not sure why/how this decoding error is happening

Answer 1

On the basis of what you shared with us, the response is not what you said you expected. To determine what went wrong, we should add some diagnostics.

So, to diagnose this, you should print the contents of the data . You should also capture and print the response .

func fetch<T: Decodable>(type: PrintifyRequestType) async throws -> T {
    let request = type.getRequest()
    
    let (data, response) = try await URLSession.shared.data(for: request)
    
    do {
        guard
            let response = response as? HTTPURLResponse,
            200...299 ~= response.statusCode
        else {
            throw URLError(.badServerResponse)
        }
            
        let decoder = JSONDecoder()
        return try decoder.decode(T.self, from: data)
    } catch {
        print("data: \(String(data: data, encoding: .utf8) ?? "cannot represent as string")")
        print("response: \(String(describing: response))")
        print(error)
        throw error
    }
}

While we're here, we should probably re- throw the error and change the return type to not be optional.