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以下是自定义结构。我想存储 [details] 的自定义结构数组。我无法将 [详细信息] 存储在文件中。在编写此 [文件中的详细信息时，应用程序正在崩溃“无效的 json 格式”

struct details : Identifiable {
    let id  = UUID()
    var name : String?
    var time : String?
    var msg : [MsgDetails]?
    var loc : String?
    var type : String?
}

在文件中写入：msgArray 是详细信息数组。msgArray = [详细信息]。

extension Array {
    var jsonStringRepresentation: String? {
        let jsonData = try? JSONSerialization.data(withJSONObject: self, options: [])
        guard jsonData != nil else {return nil}
        let jsonString = String(data: jsonData!, encoding: .utf8)
        guard jsonString != nil else {return nil}
        return jsonString! as String

    }
}

在下面的代码中 NSKeyedArchiver.archivedData 返回 nil 

if let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first{
            let fileURL = dir.appendingPathComponent(self.fileName)
            let data = try? NSKeyedArchiver.archivedData(withRootObject: msgArray.jsonStringRepresentation!, requiringSecureCoding: true)
            do {
                try data!.write(to: fileURL)
            } catch let error {
                print("\(error.localizedDescription)")
            }
        }
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1 回答 1

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您可以使用Codable而不是NSKeyedArchiver将模型转换为数据并写入文件。假设您的模型仅包含基本类型，您所要做的就是遵守Codable协议。

struct Details : Identifiable, Codable {
    ...
}

写入文件：

extension Array where Element: Encodable {

    func saveToFile(fileName: String) throws {
        do {
            let data = try JSONEncoder().encode(self)
            if let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
                let fileURL = dir.appendingPathComponent(fileName)
                try data.write(to: fileURL)
            } else {
                //throw some error
            }
        } catch {
            throw error
        }
    }

}

保存的文件可以这样读取：

func readFile(fileName: String) throws {
    do {
        if let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
            let url = dir.appendingPathComponent(fileName)
            let data = try Data(contentsOf: url)
            let decoded = try JSONDecoder().decode([Details].self, from: data)
            print("decoded: ", decoded)
        } else {
            //throw some error
        }
    } catch {
        throw error
    }

}

如果您可以将UIImage模型中的替换为Data，Codable则可以自动实现一致性。UIImage从使用中获取 imageData image.pngData()。

struct MsgDetails: Codable {
    var imageData: Data?
    var text: String?
    var date: Date?

    var image: UIImage? {
        if let data = imageData {
            return UIImage(data: data)
        }
        return nil
    }
}
于 2020-04-14T06:32:50.490 回答