json - 打开应用程序时如何加载数据？

Question

我写的代码是正确的，但由于某些原因，在调用fetchData() 方法后，superHero 数组仍然为空。我做错了什么？

class MainViewController: UICollectionViewController {

    private var superHeroes = [SuperHero]()

    let url = "https://cdn.rawgit.com/akabab/superhero-api/0.2.0/api/all.json"

    override func viewDidLoad() {
        super.viewDidLoad()

        fetchData()
    }

    // MARK: UICollectionViewDataSource

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return superHeroes.count
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! CollectionViewCell

        let superHeroe = superHeroes[indexPath.row]
        cell.configureCell(superHero: superHeroe)


        return cell
    }

    func fetchData() {

        guard let url = URL(string: url) else { return }

        URLSession.shared.dataTask(with: url) { (data, _, _) in

            guard let data = data else { return }

            do {
                self.superHeroes = try JSONDecoder().decode([SuperHero].self, from: data)
                print(self.superHeroes)
            } catch let error {
                print(error)
            }
        }.resume()
    }
}

Answer 1

因为你还没有发布你的SuperHero Codable 我根据你的JSON 从HERE 创建了一个新的.它看起来像:

typealias SuperHero = [SuperHeroElement]

struct SuperHeroElement: Codable {
    let id: Int
    let name, slug: String
    let powerstats: Powerstats
    let appearance: Appearance
    let biography: Biography
    let work: Work
    let connections: Connections
    let images: Images
}

struct Appearance: Codable {
    let gender: Gender
    let race: String?
    let height, weight: [String]
    let eyeColor, hairColor: String
}

enum Gender: String, Codable {
    case empty = "-"
    case female = "Female"
    case male = "Male"
}

struct Biography: Codable {
    let fullName, alterEgos: String
    let aliases: [String]
    let placeOfBirth, firstAppearance: String
    let publisher: String?
    let alignment: Alignment
}

enum Alignment: String, Codable {
    case bad = "bad"
    case empty = "-"
    case good = "good"
    case neutral = "neutral"
}

struct Connections: Codable {
    let groupAffiliation, relatives: String
}

struct Images: Codable {
    let xs, sm, md, lg: String
}

struct Powerstats: Codable {
    let intelligence, strength, speed, durability: Int
    let power, combat: Int
}

struct Work: Codable {
    let occupation, base: String
}

接下来您需要更换:

private var superHeroes = [SuperHero]()

与

private var superHeroes: SuperHero?

并在您的 fetchData 方法中替换

self.superHeroes = try JSONDecoder().decode([SuperHero].self, from: data)

与

self.superHeroes = try JSONDecoder().decode(SuperHero.self, from: data)

这里的 superHeroes 是 SuperHeroElement 的 Array，因此您可以通过索引从中访问数据。喜欢

guard let response = self.superHeroes else {return}
print(response[0].images) //Accessing data at 0 index

一旦您从主队列中的服务器获取数据，您还需要重新加载您的 Collection View ，例如:

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