WebImage不更新视图- SwiftUI (Xcode12)

Question

我的问题是，当我将观察到的对象字符串属性更改为另一个值时，它会更新JSON Image值(使用Unsplash API)并打印出更新后的值，但WebImage (来自SDWebImageSwiftUI)没有更改。

结果应用于的结构：

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
}

以下是视图，其中包含应该更新的webImage：

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()
    }
}

下面是我如何更改按钮中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

事实证明，您更新了搜索文本，但不再搜索。看这个能起到作用：

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对象的一个实例。考虑让它成为一个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

导入SwiftUI

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

使用它甚至更简单：

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

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

以下是包含更改的代码，并按预期工作:我对所做的更改添加了注释

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。请注意，在搜索时，您只需将结果添加到数组中，而不是删除旧的结果。这就是为什么你在更新后仍然可以看到第一张图片的原因。新的只会被附加到底部。向下滚动查看它们。如果您不想这样，只需在search上清空结果数组即可