SwiftUI 将 Int 值传递给 ViewModel

Question

我试图将 Int 传递给 ViewModel，但它不起作用。 Value还是0。Strings或者Data对象没有问题，但是Int、Double等数字值还是0值。我也试过这种方法：

@Published var tankCapacity: Int?

但还是一样。如何解决？使用字符串并转换为给定类型？

AddVehicleView: 

import SwiftUI

struct AddVehicleView: View {

@ObservedObject var viewModel: AddVehicleViewModel
@State private var selected = 0
@State private var showingAlert = false

init(viewModel: AddVehicleViewModel) {
    self.viewModel = viewModel
    UITableView.appearance().backgroundColor = .clear
    UITableView.appearance()
}

var body: some View {
    
    VStack(alignment: .leading) {
        
        Text("Add new vehicle")
            .font(.system(size: 26, weight: .medium))
            .padding(.top, -30)
            .padding(.leading, 20)
        
        VStack {
            
            TextField("Brand/Model etc", text: $viewModel.name)
                .padding(.top, 10)
                .padding(.leading, 20)
                .padding(.trailing, 20)
                .font(.system(size: 20))
                .textFieldStyle(RoundedBorderTextFieldStyle())
            
            TextField("Capacity", value: $viewModel.tankCapacity, formatter: NumberFormatter()) // I am trying send int value from here
                .padding(.top, 30)
            .padding(.leading, 20)
            .padding(.trailing, 20)
            .font(.system(size: 20))
            .textFieldStyle(RoundedBorderTextFieldStyle())
            
            Form {
                Section {
                    Picker("Fuel type", selection: $viewModel.fuelType) {
                        ForEach(0 ..< viewModel.fuels.count) {
                            Text(self.viewModel.fuels[[=10=]]).tag([=10=])
                                .padding(.leading, 5)
                                .padding(.trailing, 5)
                        }
                    }
                }
            }
            .padding(.leading, 5)
            .padding(.trailing, 5)
            
            Button("Add") {
                if self.viewModel.name.isEmpty {
                    self.showingAlert = true
                }
                else {
                    self.viewModel.saveVehicle()
                    self.viewModel.name = ""
                }
                
            }
            .frame(width: 200, height: 50)
                .background(Color.blue)
                .font(.system(size: 20, design: .default))
                .foregroundColor(Color.white)
            .cornerRadius(10)
            .padding(.top, -350)
                .alert(isPresented: $showingAlert) {
                    Alert(title: Text("Warning!"), message: Text("Fill the fields"))
            }
        }
        Spacer()
        
    }
}
}

导入基金会

class AddVehicleViewModel: ObservableObject {

@Published var name = ""
@Published var tankCapacity = 0 // and here I am trying to get value.
@Published var fuelType = 0
@Published var fuels = ["Petrol", "Diesel"]

private let persistenceService: PersistenceServiceProtocol

init(persistenceService: PersistenceServiceProtocol) {
    self.persistenceService = persistenceService
}

func saveVehicle() {
    print("name: \(name)")
    print("tankCapacity: \(tankCapacity)")
    let vehicle = Vehicle(name: name,
                          tankCapacity: tankCapacity)
    
    do {
        try self.persistenceService.addVehicle(vehicle: vehicle)
    }
    catch {
        print("ADDVEHICLEMODEL saveVehicle Error")
    }
}
}

Answer 1

您需要在调用 saveVehicle 之前先提交 TextField（通过按回车键）。

如果您改为在视图模型中执行以下操作：

@Published var tankCapacityText = "" {
    didSet {
        tankCapacity = Int(tankCapacityText) ?? 0
    }
}
@Published var tankCapacity = 0

在您看来：

TextField("Capacity", text: $vm.tankCapacityText)

那么用户就不需要回车了。

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