Unable to read JSON from rest API - json

Question

Trying to read this JSON Data:
{
"userId": 1,
"id": 1,
"title": "delectus aut autem",
"completed": false
}
But my app keeps crashing and I'm struggling to understand why (still fairly new to swift). I think the data is stored in a dictionary and I'm just handling it incorrectly. Could someone please explain the correct way to decode this JSON and how I would show it on the view? I tried JSONSerialization in place of JSONDecoder but got the same results so not sure if that's the right direction.
Model:
struct Model: Codable{
var userId: Int? = nil
var id: Int? = nil
var title: String? = nil
var completed: Bool? = nil
enum CodingKeys: CodingKey{
case userId, id, title, completed
}
}
JSON Load Function:
func loadData(){
let url = URL(string: "https://jsonplaceholder.typicode.com/todos/1")!
//create url request
var request = URLRequest(url: url)
//specify the method to use
request.httpMethod = "GET"
//set HTTP request Header, can set more than one.
request.setValue("application/json", forHTTPHeaderField: "Accept")
//send the request
let dataTask = URLSession.shared.dataTask(with: request){ data, response, error in
if let data = data{
if let users = try? JSONDecoder().decode(Model.self, from: data){
DispatchQueue.main.async {
self.dataInfo = users
}
}else{
print("Data Not Got")
}
}
if let response = response{
print("Response Got")
}
if let error = error{
print("\(error)")
}
}
dataTask.resume()
}
Swift UI View:
struct ContentView: View {
#State var dataInfo = Model()
var body: some View {
VStack{
Button("Go"){
loadData()
}
Text(dataInfo.title!)
}

Answer 1

By using ! after title, you're doing what is called a "force unwrap" -- telling the system that although the variable/property is declared as an Optional (in this case String?) that you're going to guarantee that it is not nil and there is in fact a value there. The problem is, before you've done the API call, that property is in fact nil, causing your program to crash.
Here's one way to change it (explanation follows):
struct Model: Codable{
var userId: Int
var id: Int
var title: String
var completed: Bool
}
struct ContentView: View {
#State var dataInfo : Model?
var body: some View {
VStack{
Button("Go"){
loadData()
}
if let dataInfo = dataInfo {
Text(dataInfo.title)
}
}
}
func loadData() {
// your previous code here
}
}
In this version, dataInfo is an Optional, and it gets set when the API call is made. Then, if let dataInfo = dataInfo does something called "optional binding," basically telling the system to only run the following code in the event that dataInfo isn't nil.
Finally, I've changed your Model to have non-Optional properties, since the API call you're using returns values for all of those fields. If you wanted to keep your previous model, you'd probably want to change my code to something like:
if let title = dataInfo?.title {
Text(title)
}
Check out the Swift Programming Language book for more information on Optionals and how to use them: https://docs.swift.org/swift-book/LanguageGuide/TheBasics.html