Swift - JSON解码返回空数组

Question

对于我的第一个 Swift UIKit 应用程序，我正在尝试解析一些 JSON 数据并使用它来填充 UITableView。理想情况下，表格视图会随着 JSON 的更改而更新，但目前这并不是完全必要的，因为 JSON 不会经常更改。

但我在解析 JSON 时遇到了一些问题 - 我似乎得到了一个空数组...

我的主视图控制器中的代码

import Foundation
import UIKit

//TODO - JSON

struct Visualisation: Codable {
    var id: Int
    let name, info, url_name, tags: String
}

/*
JSON:

[
    {
        "id": 0,
        "name": "Two Body Collision",
        "info": "A 2D body collision under the elastic collision assumption",
        "url_name": "https://www.imperialvisualisations.com/visualisations/two-body-collision/two-body-collision/",
        "tags": "Physics, Mechanics"

    },
    {
        "id": 1,
        "name": "Waves in Dielectrics",
        "info": "The effect of incidence angle & refractive index of dielectric on reflection & transmission",
        "url_name": "https://www.imperialvisualisations.com/visualisations/2d-and-3d-coordinate-systems/2d-polar-coordinates/",
        "tags": "Physics, Maths, Matrices, Linear algebra"
    }
]

This is the structure I am aiming for:

var visualisations: [Visualisation] = [
    .init(id:0, name: "Two Body Collision", info: "A 2D body collision under the elastic collision assumption", url_name: "https://www.imperialvisualisations.com/visualisations/two-body-collision/two-body-collision/", tags: "Physics, Mechanics"),
    .init(id:2, name: "Waves in Dielectrics", info: "The effect of incidence angle & refractive index of dielectric on reflection & transmission", url_name: "https://www.imperialvisualisations.com/visualisations/single-wave-in-3d/boundry-conditions/", tags: "Physics, Electromagnetism, Light, Refractive index, Angle of incidence")
]

 */

class ViewController: UIViewController {

    @IBOutlet weak var tableView: UITableView!


    var visualisations = [Visualisation]()

    override func viewDidLoad() {
        super.viewDidLoad()

        guard let url = URL(string: "https://api.myjson.com/bins/1ao7in") else { fatalError("JSON URL not found") }

        URLSession.shared.dataTask(with: url) { (data, _, _) in
            guard let data = data else { fatalError("JSON data not loaded") }

            guard let decodedVisualisations = try? JSONDecoder().decode([Visualisation].self, from: data) else { fatalError("Failed to decode JSON")}

            DispatchQueue.main.async{
                self.visualisations = decodedVisualisations
            }

        }.resume()

        print("visualisations")
        print(visualisations)

        tableView.delegate = self
        tableView.dataSource = self


        navigationController?.navigationBar.prefersLargeTitles = true
        title = "Visualisations"

    }

}

extension ViewController: UITableViewDataSource, UITableViewDelegate {

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

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        //visualisation at row in view
        let visualisation = visualisations[indexPath.row]
        //recast! ??
        let cell = tableView.dequeueReusableCell(withIdentifier: "TableViewCell") as! TableViewCell

        cell.setCell(visualisation: visualisation)

        //set Cell just sets the elements of the table cell in another file

        return cell

    }
}

我没有收到任何错误消息，但是解码似乎对“可视化”数组没有任何作用。

任何帮助将不胜感激 - 谢谢。

Answer 1

根据@vadian 的评论，这很好用。

struct Visualisation: Codable {
    var id: Int
    let name, info, url_name, tags: String
}

class ViewController: UIViewController {

    var visualisations = [Visualisation]()

    override func viewDidLoad() {
        super.viewDidLoad()

        guard let url = URL(string: "https://api.myjson.com/bins/1ao7in") else { fatalError("JSON URL not found") }

        URLSession.shared.dataTask(with: url) { (data, _, _) in
            guard let data = data else { fatalError("JSON data not loaded") }

            do {
                let decodedVisualisations = try JSONDecoder().decode([Visualisation].self, from: data)
                self.visualisations = decodedVisualisations
            } catch let error {
                debugPrint(error.localizedDescription)
            }
        }.resume()

    }
}