Update list after HTTP POST request in SwiftUI - xcode

Question

I want to add an object to a local server and then see the updated list in my view.
I have a ViewModelClass that handles the REST requests:
class CupcakeViewModel : ObservableObject {
let objectWillChange = PassthroughSubject<CupcakeViewModel,Never>()
init() {
get()
}
var cupcakes : [Cupcake] = [Cupcake]() {
didSet {
objectWillChange.send(self)
}
}
static let url = URL(string: "http://localhost:1337/cupcakes")!
func get() {
URLSession.shared.dataTask(with: CupcakeViewModel.url) { (data, response, error) in
if let data = data {
do {
print(data)
let cupcakes = try JSONDecoder().decode([Cupcake].self, from: data)
DispatchQueue.main.async {
self.cupcakes = cupcakes
}
} catch {
print("ERROR")
}
}
}.resume()
}
func post(cupcake : Cupcake) {
AF.request(CupcakeViewModel.url, method: .post, parameters: cupcake, encoder: JSONParameterEncoder.default).responseDecodable { (response: DataResponse<Cupcake, AFError>) in
if let value = response.value {
DispatchQueue.main.async {
self.cupcakes.append(value)
}
}
}
}
}
and in my MainView I have:
struct CupcakesView: View {
#ObservedObject var VM = CupcakeViewModel()
#State var showed = false
var body: some View {
NavigationView {
List(VM.cupcakes,id:\.self) {cupcake in
Text(cupcake.gusto)
}.padding(.top,1)
.sheet(isPresented: $showed, content: {
AggiungiCupcake(showed: self.$showed)
})
.navigationBarItems(trailing:
Button(action: {
self.showed = true
}) {
Text("ADD")
}
)
}
}
}
struct AggiungiCupcake : View {
#State var gusto = ""
#State var prezzo : Float = 0
#Binding var showed : Bool
#ObservedObject var VM = CupcakeViewModel()
var body : some View {
VStack {
TextField("Gusto", text: $gusto)
TextField("Prezzo", value: $prezzo, formatter: NumberFormatter())
Button(action: {
let c = Cupcake(gusto: self.gusto, prezzo: self.prezzo)
self.VM.post(cupcake: c)
self.showed = false
}) {
Text("ADD")
}
}.padding(30)
}
}
Both the get and the post requests go fine and on my server everything is updated, but my view does not add the new Object in the list. I use AlamoFire (AF) for the post request.
Anyone can help?

Answer 1

I think the issue is probably that you are calling send on your publisher in a didSet observer, rather than in a willSet observer. As the publisher name implies, you need to do this before your changes are made.
Try changing:
didSet {
objectWillChange.send(self)
}
to this:
willSet {
objectWillChange.send(self)
}