我无法弄清楚如何使用 SwiftUI 在文档目录中保存数据(多个属性)。我知道两种变体,第一种 - 当你有一个数组属性并且效果很好时,这里的问题 - 我不知道如何向它添加其他属性。或者,为一个项目的每个属性创建大约 3 个这样的 swift-files 是正常的。
1 个变体,保存在文档目录中:
class Stack: ObservableObject {
@Published var cards: [Card]
static let saveKey = "SavedCards"
init() {
self.cards = []
if let data = loadFile() {
if let decoded = try? JSONDecoder().decode([Card].self, from: data) {
self.cards = decoded
return
}
}
}
func add(card: Card) {
cards.insert(card, at: 0)
save()
}
func save() {
if let encoded = try? JSONEncoder().encode(cards) {
saveFile(data: encoded)
}
}
private func saveFile(data: Data) {
let url = getDocumentsDirectory().appendingPathComponent(Self.saveKey)
do {
try data.write(to: url, options: [.atomicWrite, .completeFileProtection])
} catch let error {
print("Could not write data: " + error.localizedDescription)
}
}
func loadFile() -> Data? {
let url = getDocumentsDirectory().appendingPathComponent(Self.saveKey)
if let data = try? Data(contentsOf: url) {
return data
}
return nil
}
private func getDocumentsDirectory() -> URL {
let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
return paths[0]
}
}
第二种变体是对每个属性使用 CodingKeys。但我无法弄清楚如何在此处添加方法并在其他视图中使用它,例如通过按下按钮来保存数据。对于每次数据更改,我似乎必须一遍又一遍地在每个视图中进行编码和解码。这似乎是错误的。
2 个带编码键的变体
class Profile: Codable, ObservableObject {
enum CodingKeys: CodingKey {
case categories, playedCards, playedRounds
}
@Published var categories: [Category] = [Category.red, .green, .blue, .yellow, .pink, .gray]
@Published var playedCards = 0
@Published var playedRounds = 0
init() { }
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
categories = try container.decode([Category].self, forKey: .categories)
playedCards = try container.decode(Int.self, forKey: .playedCards)
playedRounds = try container.decode(Int.self, forKey: .playedRounds)
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(categories, forKey: .categories)
try container.encode(playedCards, forKey: .playedCards)
try container.encode(playedRounds, forKey: .playedRounds)
}
}
所以我的问题是如何使用具有多个变量的 1 个变体。或者,如果我应该使用第二个变体,我怎样才能“很好地”编码和解码来自其他视图的变量。