【SwiftUI】如何初始化一个空的struct

Question

I need some kind help in SwiftUI.

I have a model below that takes in JSON data. When I want to initialize it as an empty array, it should be simple, just stating Answers, but how can I initialize it not as an array but an empty single data set.

struct Answers: Identifiable, Decodable  {
    let id: Int
    let questionsUsersId: Int
    let reactions: [Reactions]

enum CodingKeys: String, CodingKey {
        case id = "questions_id"
        case questionsUsersId = "questions_users_id"
        case reactions = "reactions"
    }

init(from decoder: Decoder) throws {

    let container = try decoder.container(keyedBy: CodingKeys.self)

    self.id = try container.decodeIfPresent(Int.self, forKey: .id) ?? 0
    self.questionsUsersId = try container.decodeIfPresent(Int.self, forKey: .questionsUsersId) ?? 0
    self.reactions = try container.decodeIfPresent([Reactions].self, forKey: .reactions) ?? [Reactions]()
}


 }

I've tried var answer: Answers = Answers( ) but got the errors below:

//Missing argument for parameter 'from' in call
//Insert 'from: <#Decoder#>'

The reason I want to initialize it empty is because I need to hand over the default value of it when the data model is nil. (ie what should I write in the xxx?)

 @ObservedObject var receiveAnswersViewModel = ReceiveAnswersViewModel()
  //abbreviate
            NavigationLink(destination: AnswerDetailView(answer: receiveAnswersViewModel.answer ?? xxx), isActive: $shouldNavigate) {
                    
                        ForEach(myPageViewModel.answers(forFilter: selectedFilter)?.answers ?? [Answers]()) { answer in
                         
                         AnswerCell(answer: answer)
                                .gesture(TapGesture()
                                                .onEnded({ _ in
                                                    //your action here
                                    self.answersId = answer.answersId
                                    receiveAnswersViewModel.fetchAnswers(answers_id: answersId ?? 0)
                                       }))
                         }
                    }

This is what I'm trying to do above: Show several cells using NavigationLink. (Imagine that the cells are tweets.) Press one of the tweets in the list → Call fetchAnswers func in the View Model which takes the pressed tweet id as the argument → Returns the specific tweet detail info→ Put it in the Answer model → Hand it over to the View → Navigate to the Tweet Detail View.

View Model code is below:

class ReceiveAnswersViewModel: ObservableObject {
@Published var answer: Answers?

func fetchAnswers(answers_id: Int){
//abbreviate
self.answer = try JSONDecoder().decode(Answers.self, from: data)
}

Thanks in advance.

Answer 1

A reasonable way is to add a static method to create an empty instance.

By the way name the struct in singular form, an instance represents likely one Answer

struct Answer: Identifiable, Decodable  {
    let id: Int
    let questionsUsersId: Int
    let reactions: [Reactions]

    static let example = Answer(id: 0, questionsUsersId: 0, reactions: [])

...

Then you can declare

var answer = Answer.example