I have an object called Item with two attributes, name (String) and value (Double). Given an array of Items I need combine the values of all items with the same name and keep the items with no duplicates. For example, say there were 4 items in the array and two of them named "Test" and the others "Object" and "Item". "Object" and "Item" would remain in the list, but the values of the two "Test"s would be combined into one item with the same name "Test".
I've included the following code for a visual representation.
Delete the comments as you read them to clean up. They're just there to clear up any confusion. Leave a comment if you have any questions. Thanks for the help!
Content View:
import SwiftUI
import CoreData
struct ContentView: View {
@Environment(\.managedObjectContext) var managedObjContext
@ObservedObject var persistence = PersistenceController.shared
@State private var items = PersistenceController.shared.getItems()
@State var isAddViewShowing = false
var body: some View {
NavigationView{
List{
Section{
ForEach(items) { item in //Displays the list of items
HStack{
Text(String(item.name!))
Spacer()
Text(String(Int(item.value)))
}
}
.onDelete(perform: { indexSet in
deleteItem(indexSet: indexSet)
})
}
}
.navigationBarTitle("Items")
.navigationBarItems(leading: combineItemsButton, trailing: addButton)
.sheet(isPresented: $isAddViewShowing){ //displays the view to add an item
AddView()
.onDisappear(perform: {
items = persistence.getItems() //"refreshes" the list of items
})
}
}
}
var combineItemsButton: some View{
Button(action:{
//combine duplicates here
persistence.contextSave()
items = persistence.getItems()
}){
Text("Combine Duplicates")
.bold()
}
}
var addButton: some View{
Button(action:{
isAddViewShowing.toggle()
}){
Text("Add Item")
.bold()
}
}
func deleteItem(indexSet: IndexSet){
withAnimation{
indexSet.map {
items[$0]
}
.forEach(managedObjContext.delete)
persistence.contextSave()
items = persistence.getItems()
}
}
}
Add View:
struct AddView: View{
@Environment(\.dismiss) var dismiss
@ObservedObject var persistence = PersistenceController.shared
@State var name: String = ""
@State var value = ""
@State private var alertMessage = ""
@State private var showAlert = false
var body: some View{
NavigationView{
Form{
TextField("Item Name", text: $name)
TextField("Item Value", text: $value)
.keyboardType(.decimalPad)
}
.navigationBarTitle("Add Item")
.navigationBarItems(leading: dismissButton, trailing: submitButton)
}
}
var submitButton: some View{
Button(action: {
if (name == ""){ //ensures the item has a name
alertMessage="Your recipe needs a name"
showAlert.toggle()
} else {
persistence.addItem(name: name, value: Double(value) ?? 2)
dismiss()
}
}){
Text("Submit")
.bold()
}
.alert(alertMessage, isPresented: $showAlert){
Button("OK",role: .cancel){}
}
}
var dismissButton: some View{
Button(action: {
dismiss()
}){
Text("Cancel")
.bold()
}
}
}
Persistence File:
import CoreData
class PersistenceController : ObservableObject{
static let shared = PersistenceController()
let container: NSPersistentContainer
init(inMemory: Bool = false) {
container = NSPersistentContainer(name: "Test")
if inMemory {
container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
}
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
container.viewContext.automaticallyMergesChangesFromParent = true
}
func getItems() -> [Item] { //fetches items
let context = container.viewContext
var request = NSFetchRequest<Item>()
request = Item.fetchRequest()
request.entity = NSEntityDescription.entity(forEntityName: "Item", in: context)
do {
let items = try context.fetch(request)
if items.count == 0 { return []}
return items.sorted(by: {$0.name! > $1.name!})
} catch {
print("**** ERROR: items fetch failed \(error)")
return []
}
}
func addItem(name: String, value: Double){
let context = container.viewContext
let item = Item(context: context)
item.id = UUID()
item.name = name
item.value = value
contextSave()
}
func contextSave() {
let context = container.viewContext
if context.hasChanges {
do {
try context.save()
self.objectWillChange.send()
} catch {
print("**** ERROR: Unable to save context \(error)")
}
}
}
}
Data Model:
You could do this on your array directly.
Something like this.
struct Item {
var name: String
var value: Double
}
var myArray: [Item] // You load it at some point
myArray = [Item(name: "One", value: 1.0), Item(name: "Two", value: 2.0), Item(name: "One", value: 3.0)]
func itemNameInArray(theArray: [Item], theItem: Item) -> Int? {
for (i, item) in theArray.enumerated() {
if item.name == theItem.name { // May be you should test on lowercased
return i
}
}
return nil
}
var myFilteredArray = [Item] ()
for item in myArray {
if let index = itemNameInArray(theArray: myFilteredArray, theItem: item) { // Already exist
var newItem = myFilteredArray[index]
newItem.value += item.value
myFilteredArray[index] = newItem
} else { // new one
myFilteredArray.append(item)
}
}
print(myFilteredArray)
This can be optimized.
