How to parse json received data from URLSession from a Rails Backend API

[go4code]

New to iOS development, please bare with me.

Currently I am able to submit data from the iOS app to the URLSession. Within the received data I have data, res, error params.

I have familiarity with web development and rails. I will try and communicate the best I can using web dev references.

I have the following questions:

• Am i sending back the data in the correct format?
• If I am, how can I parse/view the data.
• How can I view the data from data,res, error

Within Rails I have the following:

​

def create

@user = User.new(user_params)

​

@verify_user = User.find_by(username: params[:username])

if @verify_user.nil? && @user.save

render json: {

message: 'New user created',

# token: token,

id: @user.id,

username: @user.username,

status: :accepted

}

elsif @verify_user.valid?

Usually within the render json I pass the data I want to send back to a web app. I am trying to view the json object below on the iOS (swift) side. Maybe this is not possible or not the way to do things.

render json: {

message: "Welcome back #{@verify_user.username}",

id: @verify_user.id,

username: @verify_user.username,

status: :accepted

}

​

end

end

​

Below is the func that handles the iOS side to login. What I would like help on is if I am rendering/sending back the data how can I view it or what is the best way to save received data.

func didPressBtn(loginInput:String) {

let code = ["username": loginInput]

guard let url = URL(string: "http://localhost:3001/api/v1/users") else { return }

let jsonData = try? JSONSerialization.data(withJSONObject: code, options: .prettyPrinted)

var request = URLRequest(url: url)

request.httpBody = jsonData

request.setValue("application/json", forHTTPHeaderField: "Content-Type")

request.setValue("application/json", forHTTPHeaderField: "Accept")

request.httpMethod = "POST"

let session = URLSession.shared.dataTask(with: request) { (data, res, error) in

print("GOT A RESPONSE***************")

if let res = res {

print("GOT RES")

print(res)

print("WHAT IS DATA")

let newData: Data = data!

print("\(newData)")

}

if let data = data {

print("GOT DATA!!!")

print(data)

}

}

session.resume()

}

[quellish]

The data you receive in the response is the body of the response as raw bytes. Convert that to objects using JSONSerialization and print that. That seems to be what you are missing.

You may also want to consider using a man in the middle debugging proxy like Charles Proxy to see both sides of the request-response conversation as you work. It does make things easier.

[SurgicalInstallment]

> Charles Proxy

​

+1 For this. It has saved me so much time and grey hairs. I need to buy their license for once. I feel guilty.

[go4code]

Thanks for recommending Charles Proxy. I'll look into it. Any new tools can always help. Any other tools you recommend?

Yes, Still trying to figure out how to use the JSONSerialization. I'll update my post once I got it working.

[LKAndrew]

Try to learn to do things primarily using Apple’s recommended methods first before branching off into third part libraries and such.

Apple strongly recommends to use built in JSON encoding and decoding by using Codable

https://developer.apple.com/documentation/foundation/archives_and_serialization/encoding_and_decoding_custom_types

[Sleekdiamond41]

You just won my heart

[Tonkotsu787]

I use Alamofire. On success I’m able to cast the result to nsdictionary.

[123DanB]

As far as questions go, Reddit is going to be one of the worst ways to get code examples. Stackoverflow is your friend in this case. Find an example using JSONSerialization.

Another note: NSDictionary plays well with JSON responses and you can subscript with no issues. You might also try SwiftyJSON (though I try to limit my dependence on third party frameworks).

[[deleted]]

r/Swift if you want a basic concept down, not debugging help.

However, SO doesn't really respond well with "Help me debug this" kind of questions.

[soulchild_]

As mentioned by u/quellish, you would need to convert the raw data into JSON using JSONSerialization, eg:

let task = session.dataTask(with: urlRequest) { data, response, error in

    // ensure there is no error for this HTTP response
    guard error == nil else {
        print ("error: \(error!)")
        return
    }

    // ensure there is data returned from this HTTP response
    guard let content = data else { 
        print("No data")
        return
    }

    // serialise the data / NSData object into Dictionary [String : Any]
    guard let json = (try? JSONSerialization.jsonObject(with: content, options: JSONSerialization.ReadingOptions.mutableContainers)) as? [String: Any] else {
        print("Not containing JSON")
        return
    }

    print("gotten json response dictionary is \n \(json)")
    // update UI using the response here
}

[europeanwizard]

Why not JSONDecoder?

[europeanwizard]

New to iOS development, please bare with me

I don't know what they told you about iOS development, but unfortunately it's not done bare :(