WebImage未更新视图-SwiftUI（Xcode 12）

Question

我的问题是，当我将observed objects string属性更改为另一个值时，它会更新JSON映像值（使用Unsplash API)，打印出更新的值，但WebImage（来自SDWebImagesWiFTUI)不会更改。

结果应用于得结构：

struct Results : Codable {
    var total : Int
    var results : [Result]
}

struct Result : Codable {
    var id : String
    var description : String?
    var urls : URLs
}

struct URLs : Codable {
    var small : String
}

下面是包含要更新的webImage的视图：

struct MoodboardView: View {
    @ObservedObject var searchObjectController = SearchObjectController.shared
    
    var body: some View {
        
        List {
            VStack {
                Text("Mood Board: \(searchObjectController.searchText)")
                    .fontWeight(.bold)
                    .padding(6)
                ForEach(searchObjectController.results, id: \.id, content: { result in
                    Text(result.description ?? "Empty")
                    WebImage(url: URL(string: result.urls.small) )
                        .resizable()
                        .frame(height:300)
                    })
                }.onAppear() {
                searchObjectController.search()
            }
            
        }
    }
}   

下面是执行API请求的类：

class SearchObjectController : ObservableObject {
    static let shared = SearchObjectController()
    private init() {}
    
    var token = "gQR-YsX0OpwkYpbjhPVi3b4kSR-DtWrR5phwDm2kPMM"
    @Published var results = [Result]()
    @Published var searchText : String = "forest"
    
    func search () {
        let url = URL(string: "https://api.unsplash.com/search/photos?query=\(searchText)")
        var request = URLRequest(url: url!)
        request.httpMethod = "GET"
        request.setValue("Client-ID \(token)", forHTTPHeaderField: "Authorization")
        print("request: \(request)")
        
        let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
            guard let data = data else {return}
            print(String(data: data, encoding: .utf8)!)

            do {
                let res = try JSONDecoder().decode(Results.self, from: data)
                DispatchQueue.main.async {
                    self.results.append(contentsOf: res.results)
                }
                //print(self.results)
            } catch {
                print("catch: \(error)")
            }
        }
        task.resume()
    }
}

下面是我如何在一个按钮中更改searchText的值，如果你想看的话：

struct GenerateView: View {
    
    @ObservedObject var searchObjectController = SearchObjectController.shared
    
    @State private var celsius: Double = 0
    
    var body: some View {
        ZStack {
            Color.purple
                .ignoresSafeArea()
            VStack{
                
                Text("Generate a Random Idea")
                    .padding()
                    .foregroundColor(.white)
                    .font(.largeTitle)
                    .frame(maxWidth: .infinity, alignment: .center)
                    
                Image("placeholder")
                Slider(value: $celsius, in: -100...100)
                    .padding()
                Button("Generate") {
                    print("topic changed to\(searchObjectController.searchText)")
                    
                    searchObjectController.searchText.self = "tables"
                }
                Spacer()
            }
        }
    }
}

Answer 1

结果是您更新了搜索文本，但没有再次搜索。看这就有窍门了：

Button("Generate") {
    print("topic changed to\(searchObjectController.searchText)")

    searchObjectController.searchText.self = "tables" // you changed the search text but didnt search again
    self.searchObjectController.search() // adding this does the trick
}

还有。我更新了您的代码以使用EnvironmentObject。如果您在整个应用程序中使用一个对象的实例。考虑让它成为environmentObject,这样就不必一直传递它。

添加它很容易。将其添加到@main场景中

快速导入TUI

@main
struct StackoverflowApp: App {
    
    @ObservedObject var searchObjectController = SearchObjectController()
    
    var body: some Scene {
        WindowGroup {
            ContentView().environmentObject(self.searchObjectController)
        }
    }
}

而且使用起来更简单：

struct MoodboardView: View {
    
    // Env Obj. so we reference only one object
    @EnvironmentObject var searchObjectController: SearchObjectController

    var body: some View {
        
        Text("")
    }
}

下面是您的代码，它与所做的更改和预期的工作一样：我在所做的更改中添加了注释

struct ContentView: View {
    
    var body: some View {
        MoodboardView()
    }
}

struct GenerateView: View {

    @EnvironmentObject var searchObjectController: SearchObjectController

    @State private var celsius: Double = 0

    var body: some View {
        ZStack {
            Color.purple
                .ignoresSafeArea()
            VStack{
                
                Text("Generate a Random Idea")
                    .padding()
                    .foregroundColor(.white)
                    .font(.largeTitle)
                    .frame(maxWidth: .infinity, alignment: .center)
                    
                Image("placeholder")
                Slider(value: $celsius, in: -100...100)
                    .padding()
                Button("Generate") {
                    print("topic changed to\(searchObjectController.searchText)")
                    
                    searchObjectController.searchText.self = "tables" // you changed the search text but didnt search again
                    self.searchObjectController.search() // adding this does the trick
                    
                }
                Spacer()
            }
        }
    }

}

class SearchObjectController : ObservableObject {
    
    //static let shared = SearchObjectController() // Delete this. We want one Object of this class in the entire app.
     
    //private init() {} // Delete this. Empty Init is not needed

    var token = "gQR-YsX0OpwkYpbjhPVi3b4kSR-DtWrR5phwDm2kPMM"
    @Published var results = [Result]()
    @Published var searchText : String = "forest"

    func search () {
        let url = URL(string: "https://api.unsplash.com/search/photos?query=\(searchText)")
        var request = URLRequest(url: url!)
        request.httpMethod = "GET"
        request.setValue("Client-ID \(token)", forHTTPHeaderField: "Authorization")
        print("request: \(request)")
        
        let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
            guard let data = data else {return}
            print(String(data: data, encoding: .utf8)!)

            do {
                let res = try JSONDecoder().decode(Results.self, from: data)
                DispatchQueue.main.async {
                    self.results.append(contentsOf: res.results)
                }
                //print(self.results)
            } catch {
                print("catch: \(error)")
            }
        }
        task.resume()
    }
}

struct MoodboardView: View {
    
    // Env Obj. so we reference only one object
    @EnvironmentObject var searchObjectController: SearchObjectController

    var body: some View {
        
        List {
            VStack {
                Text("Mood Board: \(searchObjectController.searchText)")
                    .fontWeight(.bold)
                    .padding(6)
                ForEach(searchObjectController.results, id: \.id, content: { result in
                    Text(result.description ?? "Empty")
                    WebImage(url: URL(string: result.urls.small) )
                        .resizable()
                        .frame(height:300)
                    })
                }.onAppear() {
                searchObjectController.search()
            }
            
            // I added your update button here so I can use it.
            GenerateView()
        }
    }
}

struct Results : Codable {
    var total : Int
    var results : [Result]
}

struct Result : Codable {
    var id : String
    var description : String?
    var urls : URLs
}

struct URLs : Codable {
    var small : String
}

ps.请不要在搜索时出现，只需将结果追加到数组中，而不要删除旧的。这就是为什么更新后仍然会看到第一个图像的原因。新的只是被附加在底部。向下滚动查看它们。如果您不想这样做，只需在search上用结果清空数组即可