如何在使用 Realm 时实现 Codable

Question

我正在开发使用 Realm 和 Alamofire 的应用程序。我很高兴在我的 iOS 项目中使用这些库。

但是我必须发布一个包含多个模型列表的模型列表。所以这太深奥了，我的意思是 List inside List 包含模型，而那些模型包含几个模型的列表

为了演示，让我们以我的模型为例

@objcMembers public class MyModel : Object{
    dynamic var Id: String = ""
    dynamic var Name: String = ""
    dynamic var Favorites: List<String>? = nil 
    dynamic var Subjects: List<UserSubject>? = nil 
}


@objcMembers public class UserSubject: Object{
    dynamic var Id: String = ""
    dynamic var Name: String = ""
    dynamic var Teachers: List<Publications>? = nil 
}


@objcMembers public class Publications: Object{
    dynamic var Id: String = ""
    dynamic var Name: String = ""
    dynamic var Editors: List<Editors>? = nil 
}

所以你可以看到这些是列表中的模型，其中包含另一个模型列表。

由于 Realm，我使用 List 作为列表来创建 RelationShip。

问题： 但是现在当我尝试在 Models/Struct 上实现 Codable 时，它​​真的无法识别 List 属性。

我真的不知道如何解决这个问题？有人知道怎么做吗？

更新： 我使用的是 Swift 4.0，基础 sdk 是 11.2

Answer 1

我可以建议你使用Unrealm。
它是一个强大的库，可让您将 Swift 原生类型（结构、枚举、Arrays、Dictionaries）保存到 Realm 数据库中。所以你不必再担心 Lists 和 Codable 的兼容性了。

An example model with Codable implementation

Answer 2

在一个项目中遇到了同样的问题，写了这些扩展：

import Foundation
import RealmSwift

extension RealmSwift.List: Decodable where Element: Decodable {
    public convenience init(from decoder: Decoder) throws {
        self.init()
        let container = try decoder.singleValueContainer()
        let decodedElements = try container.decode([Element].self)
        self.append(objectsIn: decodedElements)
    }
}

extension RealmSwift.List: Encodable where Element: Encodable {
    public func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        try container.encode(self.map { $0 })
    }
}

通过这些扩展，您可以轻松地使领域对象可编码。像这样

@objcMembers public class MyModel: Object, Codable {
    dynamic var id: String = ""
    dynamic var name: String = ""
    var favorites = List<String>()
    var subjects = List<UserSubject>()
}

@objcMembers public class UserSubject: Object, Codable {
    dynamic var id: String = ""
    dynamic var name: String = ""
    var teachers = List<Publications>()
}


@objcMembers public class Publications: Object, Codable {
    dynamic var id: String = ""
    dynamic var name: String = ""
    var editors = List<Editor>()
}

@objcMembers public class Editor: Object, Codable {

}

Answer 3

您可以使用列表的扩展名

斯威夫特 4.1

extension List: Decodable  where Element: Decodable {
    public convenience init(from decoder: Decoder) throws {
    // Initialize self here so we can get type(of: self).
    self.init()
    assertTypeIsDecodable(Element.self, in: type(of: self))
    let metaType = (Element.self as Decodable.Type) // swiftlint:disable:this force_cast

    var container = try decoder.unkeyedContainer()
    while !container.isAtEnd {
        let element = try metaType.init(__from: &container)
        self.append(element as! Element) // swiftlint:disable:this force_cast
    }
  }
}

extension List: Encodable where Element: Decodable {
    public func encode(to encoder: Encoder) throws {
       assertTypeIsEncodable(Element.self, in: type(of: self))
       var container = encoder.unkeyedContainer()
       for element in self {
           // superEncoder appends an empty element and wraps an Encoder around it.
           // This is normally appropriate for encoding super, but this is really what we want to do.
           let subencoder = container.superEncoder()
           try (element as! Encodable).encode(to: subencoder) // swiftlint:disable:this force_cast
       }
   }
}

Answer 4

试试这个：

extension List: Decodable where Element: Decodable {
    public convenience init(from decoder: Decoder) throws {
        self.init()
        var container = try decoder.unkeyedContainer()
        while !container.isAtEnd {
            let element = try container.decode(Element.self)
            self.append(element)
        }
    }
}

extension List: Encodable where Element: Encodable {
    public func encode(to encoder: Encoder) throws {
        var container = encoder.unkeyedContainer()
        for element in self {
            try element.encode(to: container.superEncoder())
        }
    }
}

在这里找到它：How to use List type with Codable? (RealmSwift)