数据追加到数组后，Swiftui 视图不更新列表

如何解决数据追加到数组后，Swiftui 视图不更新列表

我有三个文件：AddAssignment、ViewAssignment 和 Task。 在 AddAssignment.swift 上单击一个按钮，它成功地将表单数据附加到 Task.swift 内的数组中。

但是，在文件 AddAssignment.swift 中，该数组中的每个项目都通过循环传递，视图无法使用新附加的数据进行更新。

AddAssignment.swift

import SwiftUI

struct AddAssignment: View {
    
    @State var taskName = ""
    @State var dueDate = ""
    @State var subject = ""
    @State var weighting = ""
    @State var totalMarks = ""
    @State var buttonClicked = false
    
    var body: some View {
        NavigationView {
            
            vstack {
                
                HStack { // Titling
                    Spacer()
                    Text("Add New Task")
                        .font(.headline)
                        .scaleEffect(2.0)
                    Spacer()
                    Image(systemName: "plus.square.fill")
                        .scaleEffect(2.0)
                    Spacer()
                }
                
                
                Form { // Gathering data
                    Section {
                        TextField("Enter task name",text: $taskName)
                        TextField("Enter due date",text: $dueDate)
                        TextField("Enter subject",text: $subject)
                    }
                    
                    Section(header: Text("Enter other task details:")) {
                        TextField("Enter task weighting",text: $weighting)
                        TextField("Enter total marks",text: $totalMarks)
                    }
                }
                
                if buttonClicked == true {
                    Text("Task Created")
                        .font(.subheadline)
                        .foregroundColor(.green)
                }
                
                Button(
                    action: {
                        data.append(Task(taskName: self.taskName,dueDate: self.dueDate,subject: self.subject,weighting: self.weighting,totalMarks: self.totalMarks))
                        buttonClicked = true
                    },label: {
                        Text("Create New Task")
                            .frame(width: 250,height: 50,alignment: .center)
                            .background(Color.blue)
                            .foregroundColor(.white)
                            .cornerRadius(8)
                    })
                    .padding()
            }
        }
        
        
        
        
    }
    
}


struct AddAssignment_Previews: PreviewProvider {
    static var previews: some View {
        AddAssignment()
            .preferredColorScheme(.light)
    }
}

Task.swift（逻辑）

import SwiftUI

struct Task: Identifiable {
    var id: String = UUID().uuidString
    var taskName: String
    var dueDate: String
    var subject: String
    var weighting: String
    var totalMarks: String
}

var data: [Task] = [
        Task(taskName: "Sample Task",dueDate: "1 Jan",subject: "Subject",weighting: "100",totalMarks: "100"),Task(taskName: "Sample Task 2",dueDate: "2 Jan",subject: "Subject B",Task(taskName: "Sample Task 3",dueDate: "3 Jan",subject: "Subject C",]

ViewAssignment.swift（发生我的错误的地方:)

import SwiftUI

struct ViewAssignment: View {
    var body: some View {
        NavigationView {
            List(data) { task in
                NavigationLink (
                    destination: TaskDetailView(),label: {
                        Image(systemName: "doc.append.fill")
                            .scaleEffect(2.5)
                            .padding()
                        
                        vstack(alignment: .leading,spacing: 3) {
                            
                            Text(task.taskName)
                                .fontWeight(.semibold)
                                .lineLimit(2)
                            
                            Text(task.dueDate)
                                .font(.subheadline)
                                .foregroundColor(.secondary)
                        }
                    })
                
                
            }
            .navigationTitle("My Tasks")
            
        }
        
    }
}




struct ViewAssignment_Previews: PreviewProvider {
    static var previews: some View {
        ViewAssignment()
    }
}

解决方法

您需要了解 SwiftUI 大量使用的 MVVM 编程范式。

因此，对于您的示例，您将拥有模型：

struct Task: Identifiable {
    var id: String = UUID().uuidString
    var taskName: String
    var dueDate: String
    var subject: String
    var weighting: String
    var totalMarks: String
}

您的观点：

struct ViewAssignment: View {
    
    // Observed to update you UI
    @ObservedObject var assignment = Assignments()
    
    var body: some View {
        NavigationView {
            VStack {
                List(self.assignment.data) { task in
                    NavigationLink (
                        destination: AdjustMe(),label: {
                            Image(systemName: "doc.append.fill")
                                .scaleEffect(2.5)
                                .padding()
                            
                            VStack(alignment: .leading,spacing: 3) {
                                
                                Text(task.taskName)
                                    .fontWeight(.semibold)
                                    .lineLimit(2)
                                
                                Text(task.dueDate)
                                    .font(.subheadline)
                                    .foregroundColor(.secondary)
                            }
                        })
                }

                // Alter your model by calling its functions
                Button(action: {
                    self.assignment.addData()
                }) {
                    Text("Add Data")
                }
            }
            
            .navigationTitle("My Tasks")
        }
        
    }
}

还有（重要的！）你的类，它包含了改变你的模型的所有函数。

// Must be ObservalbeObject
class Assignments: ObservableObject {
    // Everything that gets adjusted and needs UI update has to be marked published
    @Published var data: [Task] = [
            Task(taskName: "Sample Task",dueDate: "1 Jan",subject: "Subject",weighting: "100",totalMarks: "100"),Task(taskName: "Sample Task 2",dueDate: "2 Jan",subject: "Subject B",Task(taskName: "Sample Task 3",dueDate: "3 Jan",subject: "Subject C",]
    
    // Function to alter your model/ view
    func addData() {
        self.data.append(Task(taskName: "Sample Task 4",dueDate: "5 Jan",subject: "Subject D",weighting: "200",totalMarks: "200"))
    }
}