Running Total in SwiftUI [duplicate] - swiftui

Question

I have an app that records costs for a car. I can't work out how to create a field that keeps a running total for the ongoing costs. In the ContentView file I have a struct that defines what an expense is, which includes the 'amount'.
Any help is appreciated. Thanks.
There are 2 files, ContentView, and Addview;
struct ContentView: View {
#StateObject var expenseList = ExpenseList()
#State private var isShowingAddView = false
#State private var totalCost = 0.0
var body: some View {
NavigationView {
VStack {
VStack(alignment: .trailing) {
Text("Total Cost").font(.headline) //just holding a place for future code
}
Form {
List {
ForEach(expenseList.itemList) { trans in
HStack{
Text(trans.item)
.font(.headline)
Spacer()
VStack(alignment: .trailing) {
HStack {
Text("Amount: ")
.font(.caption).bold()
Text(trans.amount, format: .currency(code: "USD"))
.font(.caption)
}
}
}
}
.onDelete(perform: removeItems)
}
}
.navigationTitle("Expenditure")
.toolbar {
Button {
isShowingAddView = true
} label: {
Image(systemName: "plus")
}
}
.sheet(isPresented: $isShowingAddView) {
AddView(expenseList: expenseList)
}
}
}
}
func removeItems(at offsets: IndexSet) {
expenseList.itemList.remove(atOffsets: offsets)
}
}
class ExpenseList: ObservableObject {
#Published var itemList = [ExpenseItem]() {
didSet {
if let encoded = try? JSONEncoder().encode(itemList) {
UserDefaults.standard.set(encoded, forKey: "Things")
}
}
}
init() {
if let savedItems = UserDefaults.standard.data(forKey: "Things") {
if let decodedItems = try? JSONDecoder().decode([ExpenseItem].self, from: savedItems) {
itemList = decodedItems
return
}
}
itemList = []
}
}
struct ExpenseItem: Identifiable, Codable {
var id = UUID()
let item: String
let amount: Double
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
import SwiftUI
struct AddView: View {
#Environment(\.dismiss) var dismiss
#ObservedObject var expenseList: ExpenseList
#State private var item = "Fuel"
#State private var amount = 0.0
let itemType = ["Fuel", "Tyres"]
var body: some View {
NavigationView {
Form {
Picker("Type", selection: $item) {
ForEach(itemType, id: \.self) {
Text($0)
}
}
TextField("Enter amount...", value: $amount, format: .currency(code: "USD"))
}
.navigationTitle("Add an item...")
.toolbar {
Button("Save") {
let trans = ExpenseItem(item: item, amount: amount)
expenseList.itemList.append(trans)
dismiss()
}
}
}
}
}
struct AddView_Previews: PreviewProvider {
static var previews: some View {
AddView(expenseList: ExpenseList())
}
}

Answer 1

There are many ways to do ... create a field that keeps a running total for the ongoing costs. This is just one way.
Try this approach, using an extra var totalCost in your ExpenseList and a summation.
class ExpenseList: ObservableObject {
#Published private (set) var totalCost = 0.0 // <-- here
#Published var itemList = [ExpenseItem]() {
didSet {
if let encoded = try? JSONEncoder().encode(itemList) {
UserDefaults.standard.set(encoded, forKey: "Things")
}
totalCost = itemList.map{ $0.amount }.reduce(0.0, { $0 + $1 }) // <-- here
}
}
init() {
if let savedItems = UserDefaults.standard.data(forKey: "Things") {
if let decodedItems = try? JSONDecoder().decode([ExpenseItem].self, from: savedItems) {
itemList = decodedItems
return
}
}
itemList = []
}
}
And use it like this:
Text("Total Cost: \(expenseList.totalCost)").font(.headline)
You can of course do this, without adding any extra var:
Text("Total Cost: \(expenseList.itemList.map{ $0.amount }.reduce(0.0, { $0 + $1 }))")