I have this struct, :
// MARK: - JsonAPIData
struct JsonAPIData: Codable {
let data: [String: APIData]
let success: Bool
}
// MARK: - Datum
struct APIData: Codable, Identifiable {
let id = UUID()
let maxVersion, minVersion: Int
}
and I want to use these Structures to create a list of data in SwiftUI. I tried this:
struct ContentView: View {
#State var results: JsonAPIData
var body: some View {
List(results.data.values) { data in
Text("\(data)")
}
.onAppear {
self.loadData()
}
}
func loadData() {
//My code to load `results`
}.resume()
}
}
but I had this error:
Initializer 'init(_:rowContent:)' requires that 'Dictionary<String, APIData>.Values' conform to 'RandomAccessCollection'
How can I fix it for list keys and values of APIData?
you can try this: (but keep in mind: if you loop over dictionaries the order is random....)
struct JsonAPIData: Codable {
let data: [String: APIData]
let success: Bool
}
// MARK: - Datum
struct APIData: Codable, Identifiable {
let id = UUID()
let maxVersion, minVersion: Int
}
struct ContentView: View {
func getKeys() -> [String] {
return results.data.map{$0.key}
}
func getValues() -> [APIData] {
return results.data.map{$0.value}
}
#State var results: JsonAPIData
var body: some View {
List(getKeys(), id: \.self) { key in
Text("\(self.results.data[key]!.maxVersion)")
}
.onAppear {
self.loadData()
}
}
func loadData() {
//My code to load `results`
}
Related
I'm trying to build a simple SwiftUI view that displays a number of toggles. While I can get everything to display ok, I cannot get the toggles to flip. Here's is a simplified code example:
import SwiftUI
class StoreableParam: Identifiable {
let name: String
var id: String { name }
#State var isEnabled: Bool
let toggleAction: ((Bool) -> Void)?
init(name: String, isEnabled: Bool, toggleAction: ((Bool) -> Void)? = nil) {
self.name = name
self.isEnabled = isEnabled
self.toggleAction = toggleAction
}
}
class StoreableParamViewModel: ObservableObject {
#Published var storeParams: [StoreableParam] = []
init() {
let storedParam = StoreableParam(name: "Stored Param", isEnabled: false) { value in
print("Value changed")
}
storeParams.append(storedParam)
}
}
public struct UBIStoreDebugView: View {
#StateObject var viewModel: StoreableParamViewModel
public var body: some View {
VStack {
List {
ForEach(viewModel.storeParams, id: \.id) { storeParam in
Toggle(storeParam.name, isOn: storeParam.$isEnabled)
.onChange(of: storeParam.isEnabled) {
storeParam.toggleAction?($0)
}
}
}
}.navigationBarTitle("Toggle Example")
}
}
As mentioned in the comments, there are a couple of things going on:
#State is only for use in a View
Your model should be a struct
Then, you can get a Binding using the ForEach element binding syntax:
struct StoreableParam: Identifiable {
let name: String
var id: String { name }
var isEnabled: Bool
let toggleAction: ((Bool) -> Void)?
}
class StoreableParamViewModel: ObservableObject {
#Published var storeParams: [StoreableParam] = []
init() {
let storedParam = StoreableParam(name: "Stored Param", isEnabled: false) { value in
print("Value changed")
}
storeParams.append(storedParam)
}
}
public struct UBIStoreDebugView: View {
#StateObject var viewModel: StoreableParamViewModel
public var body: some View {
VStack {
List {
ForEach($viewModel.storeParams, id: \.id) { $storeParam in
Toggle(storeParam.name, isOn: $storeParam.isEnabled)
.onChange(of: storeParam.isEnabled) {
storeParam.toggleAction?($0)
}
}
}
}
}
}
I have this simple code for my model:
import Foundation
class TaskListModel: ObservableObject
{
struct TodoItem: Identifiable
{
var id = UUID()
var title: String = ""
}
#Published var items: [TodoItem]?
//MARK: - intents
func addToList()
{
self.items!.append(TodoItem())
}
}
Then I use it in this view:
import SwiftUI
struct TasksListView: View {
#ObservedObject var model = TaskListModel()
var body: some View {
List {
Button("Add list", action: {
model.addToList()
})
ForEach(model.items!) { item in
TextField("Title", text: item.title)
}
.onMove { indexSet, offset in
model.items!.move(fromOffsets: indexSet, toOffset: offset)
}
.onDelete { indexSet in
model.items!.remove(atOffsets: indexSet)
}
}
}
}
struct TasksListView_Previews: PreviewProvider {
static var previews: some View {
TasksListView()
}
}
I can't seem to make this code work, I suspect the items array needs to be wrapped in #Binding property wrapper, but it already wrapped in #Published, so it puzzles me even more. Any help would be appreciated!
You have forgotten to create array for items
class TaskListModel: ObservableObject
{
struct TodoItem: Identifiable
{
var id = UUID()
var title: String = ""
}
#Published var items: [TodoItem] = [] // << here !!
// ...
}
and remove everywhere force-unwrap (!!)
I can't figure it out why view is not updating, please help. In real project I get data via websocket (and set variable with DispatchQueue.main.async {}). Here's the code as an example. After clicking on button nothing happens with the view. I use ObservableObject, Published attributes. What's the problem?
ps. It requires to add some more text to the post, because it's mostly the code, but I don't know what to add, everything is below :)
import SwiftUI
class DataBase: ObservableObject {
#Published var data: [MyData]
#Published var users: [User]
init(data: [MyData], users: [User]) {
self.data = data
self.users = users
}
}
class MyData: ObservableObject, Identifiable {
#Published var type: String
#Published var array: [Double]
init(type: String, array: [Double]) {
self.type = type
self.array = array
}
}
class User: ObservableObject, Identifiable {
#Published var id: UUID = UUID()
#Published var name: String
#Published var data: MyData
init(name: String, data: MyData) {
self.name = name
self.data = data
}
}
let data: [MyData] = [
MyData(type: "type1", array: [1, 2, 3]),
MyData(type: "type2", array: [4, 5, 6, 7]),
]
let users: [User] = [
User(name: "Tim", data: data[0]),
User(name: "Steve", data: data[1]),
]
struct ContentView: View {
let db = DataBase(data: data, users: users)
var body: some View {
ShowView(db: db)
}
}
struct ShowView: View {
#ObservedObject var db: DataBase
var body: some View {
HStack {
List(db.users) { user in
Text("\(user.name) \(user.data.type)")
Text("\(user.data.array.count)")
Divider()
}
List(db.data) { data in
Text("\(data.type)")
Text("\(data.array.count)")
Divider()
}
}
HStack {
Button("add data to data[0]") {
db.data[0].array.append(db.data[0].array.last! + 10)
print(db.data[0].array)
}
Button("add data to data[1]") {
db.data[1].array.append(db.data[1].array.last! + 20)
print(db.data[1].array)
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
try this using objectWillChange, works for me:
struct ShowView: View {
#ObservedObject var db: DataBase
var body: some View {
HStack {
List(db.users) { user in
Text("\(user.name) \(user.data.type)")
Text("\(user.data.array.count)")
Divider()
}
List(db.data) { data in
Text("\(data.type)")
Text("\(data.array.count)")
Divider()
}
}
HStack {
Button("add data to data[0]") {
db.objectWillChange.send() // <-- here
db.data[0].array.append(db.data[0].array.last! + 10)
print(db.data[0].array)
}
Button("add data to data[1]") {
db.objectWillChange.send() // <-- here
db.data[1].array.append(db.data[1].array.last! + 20)
print(db.data[1].array)
}
}
}
}
Just make model as value type (i.e. struct instead of class) - no more changes needed:
struct MyData: Identifiable {
var id = UUID()
var type: String
var array: [Double]
init(type: String, array: [Double]) {
self.type = type
self.array = array
}
}
struct User: Identifiable {
var id: UUID = UUID()
var name: String
var data: MyData
init(name: String, data: MyData) {
self.name = name
self.data = data
}
}
Tested with Xcode 13.4 / iOS 15.5
Update
Then it is needed to create separated views with ObservedObject for every observable model object, like
List(db.users) {
UserRowView(user: $0)
}
struct UserRowView: View {
#ObservedObject var user: User // a class, so needed to be observed
var body: some View {
Text("\(user.name) \(user.data.type)")
Text("\(user.data.array.count)")
Divider()
}
}
the same for MyData, or make a dependency update, like
class User: ObservableObject {
#Published var data: MyData
// ...
private var cancellable: AnyCancellable?
init(...) {
// ....
cancellable = data.objectWillChange.sink { [weak self] _ in
guard let self = self else { return }
self.objectWillChange.send()
}
}
}
I'm struggling with some basic MVVM concepts in SwiftUI. I appreciate this is probably a simple question but my brain is frazzled I can't figure it out.
Here's my models/views/viewmodels etc.
import Foundation
struct Challenges {
var all: [Challenge]
init() {
all = []
}
}
struct Challenge: Identifiable, Codable, Hashable {
private(set) var id = UUID()
private(set) var name: String
private(set) var description: String
private(set) var gpxFile: String
private(set) var travelledDistanceMetres: Double = 0
init(name: String, description: String, gpxFile: String) {
self.name = name
self.description = description
self.gpxFile = gpxFile
}
mutating func addDistance(_ distance: Double) {
travelledDistanceMetres += distance
}
}
import SwiftUI
#main
struct ActivityChallengesApp: App {
var body: some Scene {
WindowGroup {
ChallengesView()
.environmentObject(ChallengesViewModel())
}
}
}
import SwiftUI
class ChallengesViewModel: ObservableObject {
#Published var challenges: Challenges
init() {
challenges = Challenges()
challenges.all = DefaultChallenges.ALL
}
func addDistance(_ distance: Double, to challenge: Challenge) {
challenges.all[challenge].addDistance(distance)
}
}
import SwiftUI
struct ChallengesView: View {
#EnvironmentObject var challengesViewModel: ChallengesViewModel
var body: some View {
NavigationView {
List {
ForEach(challengesViewModel.challenges.all) { challenge in
NavigationLink {
ChallengeView(challenge)
.environmentObject(challengesViewModel)
} label: {
VStack(alignment: .leading) {
Text(challenge.name)
Text("\(challenge.travelledDistanceMetres)")
}
}
}
}
.navigationTitle("Challenges")
}
}
}
import SwiftUI
struct ChallengeView: View {
var challenge: Challenge
#EnvironmentObject var challengesViewModel: ChallengesViewModel
init(_ challenge: Challenge) {
self.challenge = challenge
}
var body: some View {
VStack(alignment: .leading) {
Text(challenge.name)
Text("\(challenge.travelledDistanceMetres)")
}
.onTapGesture {
handleTap()
}
}
func handleTap() {
challengesViewModel.addDistance(40, to: challenge)
}
}
I understand the concepts but I'm confused as to what the ViewModel should be.
I feel like this is overkill, i.e. sending a model object to the view and the view model as an environment object. With this set up, I call the addDistance() function in the view model from within the view to make changes to the model.
ChallengeView(challenge)
.environmentObject(challengesViewModel)
Is it better to have a view model for the collection or one view model per model object?
This is the simplest version I could come up with.
I don't really understand the need for the challenges.all ? So I took it out.
I have
a struct for the single challenge
an observable class which is publishing the challenges array
instantiate this once with #StateObject and pass it down as you did
btw: You don't need explicit initializers for structs
this is it:
#main
struct ActivityChallengesApp: App {
// here you create your model once
#StateObject var challenges = ChallengesModel()
var body: some Scene {
WindowGroup {
ChallengesView()
.environmentObject(challenges)
}
}
}
struct Challenge: Identifiable, Codable, Hashable {
var id = UUID()
var name: String
var description: String
var gpxFile: String
var travelledDistanceMetres: Double = 0
mutating func addDistance(_ distance: Double) {
travelledDistanceMetres += distance
}
}
class ChallengesModel: ObservableObject {
#Published var challenges: [Challenge]
init() {
// Test data
challenges = [
Challenge(name: "Challenge One", description: "?", gpxFile: ""),
Challenge(name: "Challenge Two", description: "?", gpxFile: ""),
Challenge(name: "Last Challenge", description: "?", gpxFile: "")
]
}
func addDistance(_ distance: Double, to challenge: Challenge) {
// find the challenge and update it
if let i = challenges.firstIndex(where: {$0.id == challenge.id}) {
challenges[i].addDistance(distance)
}
}
}
struct ChallengesView: View {
#EnvironmentObject var challengesModel: ChallengesModel
var body: some View {
NavigationView {
List {
ForEach(challengesModel.challenges) { challenge in
NavigationLink {
ChallengeView(challenge: challenge)
.environmentObject(challengesModel)
} label: {
VStack(alignment: .leading) {
Text(challenge.name)
Text("\(challenge.travelledDistanceMetres)")
}
}
}
}
.navigationTitle("Challenges")
}
}
}
struct ChallengeView: View {
var challenge: Challenge
#EnvironmentObject var challengesModel: ChallengesModel
var body: some View {
VStack(alignment: .leading) {
Text(challenge.name)
Text("\(challenge.travelledDistanceMetres)")
}
.onTapGesture {
handleTap()
}
}
func handleTap() {
challengesModel.addDistance(40, to: challenge)
}
}
[ Ed: Once I had worked this out, I edited the title of this question to better reflect what I actually needed. - it wasn't until I answered my own question that I clarified what I needed :-) ]
I am developing an App using SwiftUI on IOS in which I have 6 situations where I will have a List of items which I can select and in all cases the action will be to move to a screen showing that Item.
I am a keen "DRY" advocate so rather than write the List Code 6 times I want to abstract away the list and select code and for each of the 6 scenarios I want to just provide what is unique to that instance.
I want to use a protocol but want to keep boilerplate to a minimum.
My protocol and associated support is this:
import SwiftUI
/// -----------------------------------------------------------------
/// ListAndSelect
/// -----------------------------------------------------------------
protocol ListAndSelectItem: Identifiable {
var name: String { get set }
var value: Int { get set }
// For listView:
static var listTitle: String { get }
associatedtype ItemListView: View
func itemListView() -> ItemListView
// For detailView:
var detailTitle: String { get }
associatedtype DetailView: View
func detailView() -> DetailView
}
extension Array where Element: ListAndSelectItem {
func listAndSelect() -> some View {
return ListView(items: self, itemName: Element.listTitle)
}
}
struct ListView<Item: ListAndSelectItem>: View {
var items: [Item]
var itemName: String
var body: some View {
NavigationView {
List(items) { item in
NavigationLink(
destination: DetailView(item: item, index: String(item.value))
) {
VStack(alignment: .leading){
item.itemListView()
.font(.system(size: 15)) // Feasible that we should remove this
}
}
}
.navigationBarTitle(Text(itemName).foregroundColor(Color.black))
}
}
}
struct DetailView<Item: ListAndSelectItem>: View {
#Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
var item: Item
var index: String
var body: some View {
NavigationView(){
item.detailView()
}
.navigationBarTitle(Text(item.name).foregroundColor(Color.black))
.navigationBarItems(leading: Button(action: {
self.presentationMode.wrappedValue.dismiss()
}, label: { Text("<").foregroundColor(Color.black)}))
}
}
which means I can then just write:
struct Person: ListAndSelectItem {
var id = UUID()
var name: String
var value: Int
typealias ItemListView = PersonListView
static var listTitle = "People"
func itemListView() -> PersonListView {
PersonListView(person: self)
}
typealias DetailView = PersonDetailView
let detailTitle = "Detail Title"
func detailView() -> DetailView {
PersonDetailView(person: self)
}
}
struct PersonListView: View {
var person: Person
var body: some View {
Text("List View for \(person.name)")
}
}
struct PersonDetailView: View {
var person: Person
var body: some View {
Text("Detail View for \(person.name)")
}
}
struct ContentView: View {
let persons: [Person] = [
Person(name: "Jane", value: 1),
Person(name: "John", value: 2),
Person(name: "Jemima", value: 3),
]
var body: some View {
persons.listAndSelect()
}
}
which isn't bad but I feel I ought to be able to go further.
Having to write:
typealias ItemListView = PersonListView
static var listTitle = "People"
func itemListView() -> PersonListView {
PersonListView(person: self)
}
with
struct PersonListView: View {
var person: Person
var body: some View {
Text("List View for \(person.name)")
}
}
still seems cumbersome to me.
In each of my 6 cases I'd be writing very similar code.
I feel like I ought to be able to just write:
static var listTitle = "People"
func itemListView() = {
Text("List View for \(name)")
}
}
because that's the unique bit.
But that certainly won't compile.
And then the same for the Detail.
I can't get my head around how to simplify further.
Any ideas welcome?
The key to this is, if you want to use a view in a protocol then:
1) In the protocol:
associatedtype SpecialView: View
var specialView: SpecialView { get }
2) In the struct using the protocol:
var specialView: some View { Text("Special View") }
So in the situation of the question:
By changing my protocol to:
protocol ListAndSelectItem: Identifiable {
var name: String { get set }
var value: Int { get set }
// For listView:
static var listTitle: String { get }
associatedtype ListView: View
var listView: ListView { get }
// For detailView:
var detailTitle: String { get }
associatedtype DetailView: View
var detailView: DetailView { get }
}
I can now define Person as:
struct Person: ListAndSelectItem {
var id = UUID()
var name: String
var value: Int
static var listTitle = "People"
var listView: some View { Text("List View for \(name)") }
var detailTitle = "Person"
var detailView: some View { Text("Detail View for \(name)") }
}
which is suitable DRY and free of boilerplate!