SwiftUI 订阅属性更改为 EnvironmentObject

Question

这是我的模型：

class Channel: Identifiable, Decodable, ObservableObject {
    
    var id = UUID()
    var channelId = ""
    var title = ""
    var thumbnail = ""
    @Published var thumbnailImage : UIImage?
    
    enum CodingKeys: String, CodingKey {
        
        //Keys not in the model
        case snippet
        case thumbnails
        case high
         
        //Keys in the model
        case channelId
        case title
        case thumbnail = "url"
    }
    
    required init (from decoder: Decoder) throws {
        
        let container =  try decoder.container(keyedBy: CodingKeys.self)
        let snippetContainer = try container.nestedContainer(keyedBy: CodingKeys.self, forKey: .snippet)
        let thumbnailsContainer = try snippetContainer.nestedContainer(keyedBy: CodingKeys.self, forKey: .thumbnails)
        let highContainer = try thumbnailsContainer.nestedContainer(keyedBy: CodingKeys.self, forKey: .high)
        
        self.title = try snippetContainer.decode(String.self, forKey: .title)
        self.thumbnail = try highContainer.decode(String.self, forKey: .thumbnail)
        self.channelId = try snippetContainer.decode(String.self, forKey: .channelId)
    }
}

class ChannelStore: ObservableObject {    
    @Published var allChannels = [Channel]()
}

我有一个链接到 ChannelStore 的 EnvironmentObject，它都按预期工作。

问题是属性 thumbnailImage 更改时我的视图需要更新。（由于它来自网络调用，视图在调用 returns 之前生成，同时使用库存图像）。我尝试将 Published 属性包装器添加到那个属性但它没有做任何事情。

在我看来我有：@EnvironmentObject var channelStore: ChannelStore

如何订阅由 EnvironmentObject 管理的属性变更？

编辑

建议将通道 class 更改为结构。我制作 class 的唯一原因是为了避免“无法分配给属性：'channel' 是一个 'let' 常量：

for channel in channelStore.allChannels {
    networking.setThumbnail(channel: channel) { image in
        channel.thumbnailImage = image
    }
}

最终评论

我能够使用下面提供的答案解决整个问题，并将我的 for 循环更改为以下内容：

for (index, var channel) in channelStore.allChannels.enumerated() {
    networking.setThumbnail(channel: channel) { image in
        channel.thumbnailImage = image
        channelStore.allChannels[index] = channel
        print("Images LOADED")
    }
}

Answer 1

如果你能让你的 Channel 成为一个 struct:

struct Channel: Identifiable, Decodable { // <- replace `class` with `struct`
    ...
    var thumbnailImage : UIImage? // <- remove `@Published`
}

然后 thumbnailImage 的每次修改都会创建 Channel 对象的新副本并触发 ChannelStore 中的 @Published 属性:

class ChannelStore: ObservableObject {
    @Published var allChannels = [Channel]()
}

SwiftUI 订阅属性更改为 EnvironmentObject

SwiftUI Subscribing to property change with EnvironmentObject

swift

swiftui

environmentobject

SwiftUI 订阅 属性 更改为 EnvironmentObject

SwiftUI Subscribing to property change with EnvironmentObject

swift

swiftui

environmentobject

SwiftUI 订阅属性更改为 EnvironmentObject