SwiftUI 将 Int 值传递给 ViewModel答案

【问题标题】：SwiftUI pass Int value to the ViewModelSwiftUI 将 Int 值传递给 ViewModel
【发布时间】：2021-06-06 15:14:47
【问题描述】：

我正在尝试将 Int 传递给 ViewModel，但它不起作用。 Value 仍然是 0。Strings 或 Data 对象没有问题，但是 Int、Double 和其他数字值仍然是 0 值。我也试过这种方式：

@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[$0]).tag($0)
                                .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()
        
    }
}
}

导入基础

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")
    }
}
}

【问题讨论】：

你在哪里修改 tankCapacity 值？
到 ViewModel。我编辑了代码。 View 和 ViewModel 粘在一起了。

标签： ios swiftui combine

【解决方案1】：

在调用saveVehicle之前，您需要先提交TextField（按回车键）。

如果您改为在视图模型中使用以下内容：

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

在你看来：

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

那么用户就不需要回车了。

【讨论】：