在Swift 4中解析JSON后，为什么会得到空白的UITableView？

Question

I can't figure out why the cells don't return with data.

I can parse normally using the Decodable, which means that is working.

I've been trying all the methods I find without success.

struct MuscleGroup: Decodable {
   let ExcerciseID: String
   let description: String
   let excerciseName: String
   let muscleGroup: String
}


class ExerciseListViewController: UITableViewController {




var muscleGroup = [MuscleGroup]()


override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return muscleGroup.count
}

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "ExerciseList", for: indexPath) as! ExcerciseList

    let muscle = muscleGroup[indexPath.row]

    cell.textLabel!.text = muscle.excerciseName
    return cell
}

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    print(self.muscleGroup[indexPath.row])
    tableView.deselectRow(at: indexPath, animated: true)
}

override func viewDidLoad() {
    super.viewDidLoad()
    self.tableView.dataSource = self
    self.tableView.delegate = self
    getJson()

}




func getJson(){

    guard let url = URL(string: "https://jsonurl") else { return }

    let session = URLSession.shared
    session.dataTask(with: url) { (data, response, error) in
        if let response = response {
            print(response)
        }

        if let data = data {
            print(data)
            do {
                let muscles = try JSONDecoder().decode([MuscleGroup].self, from: data)
                for muscle in muscles {


                    let muscleGroup = muscle.excerciseName
                    print(muscleGroup)
                    DispatchQueue.main.async {
                        self.tableView.reloadData()
                    }

                }
            } catch {
                print(error)
            }

        }
        }.resume()



}

If I change the var muscleGroup = String to ["Chest", "Back", "Abdominals","Arms", "Legs"] it returns correctly.

Also, the print result on the console returns all the data that needs to be on the Table View.

What am I doing wrong?

Answer 1

In your getJson function this line

let muscleGroup = muscle.excerciseName

is creating a new local variable called muscleGroup , change the line to be

self.muscleGroup.append(muscle.excerciseName)

ie get rid of the let and append the value to the main array variable

Also move the

 DispatchQueue.main.async {
     self.tableView.reloadData()
 }

to be outside of the for loop of muscles as you are forcing the table to reload for each entry rather than when you are finished

Answer 2

As you probably want to use the entire struct

1. Replace

    var muscleGroup = [String]() 

   with

    var muscleGroups = [MuscleGroup]() 

2. Replace

    let muscles = try JSONDecoder().decode([MuscleGroup].self, from: data) for muscle in muscles { let muscleGroup = muscle.excerciseName print(muscleGroup) DispatchQueue.main.async { self.tableView.reloadData() } } 

   with

    self.muscleGroups = try JSONDecoder().decode([MuscleGroup].self, from: data) DispatchQueue.main.async { self.tableView.reloadData() } 

3. Replace

    cell.textLabel?.text = self.muscleGroup[indexPath.row] 

   with

    cell.textLabel?.text = self.muscleGroups[indexPath.row].muscleGroup