在 swiftdata 中编写 @model 的正确方法

Question

我正在开发一个 Swift 项目，其中有两个模型类：PlaylistGroup 和 PlaylistItem。我遇到了一个问题，无法将项目附加到 PlaylistGroup 中的 playlistItems 属性。以下是模型定义：

@Model
class PlaylistGroup  {
    @Attribute(.unique) var groupNumberID = UUID()
    var groupName: String
    var playlistModel: PlayListModel?
    
    @Relationship(deleteRule: .cascade, inverse: \PlaylistItem.group)
    var playlistItems: [PlaylistItem]?
    
    init(groupName: String) {
        self.groupName = groupName
        self.playlistItems = playlistItems. // should I write this??
    }
   
}

@Model
class PlaylistItem: Hashable {
    
    var duration: Int?
    var tvgId: String?
    var tvgName: String?
    var tvgCountry: String?
    var tvgLanguage: String?
    var tvgLogo: String?
    var tvgChno: String?
    var tvgShift: String?
    var groupTitle: String
    var seasonNumber: Int?
    var episodeNumber: Int?
    var kind: String?
    var url: URL?
    var lastPlay: Date
    
    var group: PlaylistGroup?
    
    init( duration: Int? = nil, tvgId: String? = nil, tvgName: String? = nil, tvgCountry: String? = nil, tvgLanguage: String? = nil, tvgLogo: String? = nil, tvgChno: String? = nil, tvgShift: String? = nil, groupTitle: String, seasonNumber: Int? = nil, episodeNumber: Int? = nil, kind: String? = nil, url: URL? = nil, lastPlay: Date) {
        
        self.duration = duration
        self.tvgId = tvgId
        self.tvgName = tvgName
        self.tvgCountry = tvgCountry
        self.tvgLanguage = tvgLanguage
        self.tvgLogo = tvgLogo
        self.tvgChno = tvgChno
        self.tvgShift = tvgShift
        self.groupTitle = groupTitle
        self.seasonNumber = seasonNumber
        self.episodeNumber = episodeNumber
        self.kind = kind
        self.url = url
        self.lastPlay = lastPlay
    }
   
}

我应该使用 self.playlistItems = playlistItems 初始化 PlaylistGroup 初始值设定项中的 playlistItems 属性吗？我注意到，如果没有这个，我无法使用append 方法将数据附加到playlistItems。任何帮助将不胜感激！

谢谢！

Answer 1

您可以使用空数组或 nil 来初始化关系。

self.playlistItems = playlistItems.

对我来说没有意义。

在添加

playlistItems

之前，您必须将

PlaylistGroup

插入模型上下文中。如果您确实愿意，可以在其初始化程序中执行此操作。