如何在 swiftui 中动态定义可观察对象内的对象？

Question

我是 swiftui 的新手，正在学习它。

我有一种情况，我必须在可观察对象中定义一个对象数组（假设对象是 USER，所以对象数组将是“[USER]”）。这个可观察对象是一个 ViewModel。在初始化此 ViewModel 的任何其他视图中有一个 API 调用。

只有在初始化此 ViewModel 之后，我才必须初始化此 [User] 对象。我必须将此 [USER] 带入 ViewModel，因为此对象 [USER] 将由其他视图上的 TextField 修改。

由于几个编译时错误，我无法在 API 调用响应后初始化此 [USER] 对象。

struct User: Identifiable {

   var profileName: String = ""
   var profileId: String = ""   
   var firstname: String = ""
   var lastname: String = ""
}


class ViewModel: ObservableObject {

    @Published var document: Document?

    @Published var users = [User]()
    var idValue: String

    init (idValue: String) {
        idValue = idValue
    }
    
    func getDetails() {
        
        APIService.shared.getDocumentDetails(idValue: idValue) { document in
            DispatchQueue.main.async {
                self.document = document
                
                self.setEndUserValues()
            }
        }
    }
    
    func setEndUserValues() {
        
        var users = [User]()
        
        if let document = document, let subjects = document.subjects {
            ForEach(0..<subjects.count, id: \.self) { index in
                let profile = subjects[index]
                var user = User(id: index)
                
                user.profileName = profile.profileName ?? ""
                user.profileId = profile.profileId ?? ""
                user.firstname = profile.firstname ?? ""
                user.lastname = profile.lastname ?? ""
                users.append(user)

            }

        }
    }

我收到类型“()”无法符合 'View' 的错误。另外，响应是相当嵌套的，所以我没有提到更多的属性。请帮我实现这个目标。

Answer 1

您可能会发现以下代码比您的固定代码效果更好：

struct User: Identifiable {
    
    var profileName: String
    var id: String // In order to conform to Identifiable, you have to have
                   // a variable named "id"
    var firstName: String // We write Swift variables in camelcase. 
    var lastName: String  // You can even see that these get flagged as a spelling error. 
}

class ViewModel: ObservableObject {
    
    @Published var document: Document?
    
    @Published var users = [User]()
    var idValue: String
    
    init(idValue: String) { // I am not sure of the purpose of initializing the
                            // ViewModel with an "id". You shouldn't have multiple
                            // copies of this in your app.
        self.idValue = idValue
    }
    
    func getDetails() {
        APIService.shared.getDocumentDetails(idValue: idValue) { document in
            DispatchQueue.main.async {
                self.document = document
                
                self.setEndUserValues()
            }
        }
    }
    
    func setEndUserValues() {
        if let document = document, let subjects = document.subjects {
            for subject in subjects { // You have an array of Subjects. Use it directly.

                // This way of initializing creates your User and appends it to the
                // array of Users in one step.
                users.append(User(
                    profileName: subject.profileName,
                    id: subject.profileId,
                    firstName: subject.firstname,
                    lastName: subject.lastname))
            }
        }
    }
}

我想花一分钟时间展示一下我在上面修复的代码中的一些问题：

func setEndUserValues() {
    
    var users = [User]() // You are creating a local array here. This is not your
                         // "@Published var users"
    
    if let document = document, let subjects = document.subjects {
        for index in 0..<subjects.count { // This becomes unnecessary when you don't
                                          // need the index.
            let profile = subjects[index] // This becomes unnecessary.
            var user = User(id: index) // According to your User struct, this doesn't
                                       // compile. You don't have an initializer that
                                       // accepts an "id: Int"
            
            user.profileName = profile.profileName ?? ""
            user.profileId = profile.profileId ?? ""
            user.firstname = profile.firstname ?? ""
            user.lastname = profile.lastname ?? ""
            users.append(user) // This is your local array of users. This doesn't
                               // actually go anywhere, and you don't actually
                               // fill your ViewModel.users array
        }
    }
}

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