The following code creates new controls every time a button is pressed at runtime, the problem is that the picker selection is set to the same state.
How can I create new controls with different state variables so they can operate separately ?
struct ContentView: View {
#State private var numberOfControlls = 0
#State var selection: String="1"
var body: some View {
VStack {
Button(action: {
self.numberOfControlls += 1
}) {
Text("Tap to add")
}
ForEach(0 ..< numberOfControlls, id: \.self) { _ in
Picker(selection: self.$selection, label:
Text("Picker") {
Text("1").tag(1)
Text("2").tag(2)
}
}
}
}
}
How can I create new controls with different state variables so they can operate separately ?
Separate control into standalone view with own state (or view model if/when needed).
Here is a demo:
struct ContentView: View {
#State private var numberOfControlls = 0
var body: some View {
VStack {
Button(action: {
self.numberOfControlls += 1
}) {
Text("Tap to add")
}
ForEach(0 ..< numberOfControlls, id: \.self) { _ in
ControlView()
}
}
}
}
struct ControlView: View {
#State var selection: String="1"
var body: some View {
Picker(selection: self.$selection, label:
Text("Picker")) {
Text("1").tag(1)
Text("2").tag(2)
}
}
}
Related
List selection doesn’t show If I add a NavigationLink and a .contextMenu to the list, when I select a row, the selection disappears.
struct ContentView: View {
#State private var selection: String?
let names = ["Cyril", "Lana", "Mallory", "Sterling"]
var body: some View {
NavigationView {
List(names, id: \.self, selection: $selection) { name in
NavigationLink(destination: Text("Hello, world!")) {
Text(name)
.contextMenu {
Button(action: {}) {
Text("Tap me!")
}
}
}
}
.toolbar {
EditButton()
}
}
}
}
We can disable context menu button(s) for the moment of construction in edit mode (because the button is a reason of issue).
Here is a possible approach - some redesign is required to handle editMode inside context menu (see also comments inline).
Tested with Xcode 13.2 / iOS 15.2
struct ContentViewSelection: View {
#State private var selection: String?
let names = ["Cyril", "Lana", "Mallory", "Sterling"]
var body: some View {
NavigationView {
List(names, id: \.self, selection: $selection) { name in
// separated view is needed to use editMode
// environment value
NameCell(name: name)
}
.toolbar {
EditButton()
}
}
}
}
struct NameCell: View {
#Environment(\.editMode) var editMode // << !!
let name: String
var body: some View {
NavigationLink(destination: Text("Hello, world!")) {
Text(name)
}
.contextMenu {
if editMode?.wrappedValue == .inactive { // << !!
Button(action: {}) {
Text("Tap me!")
}
}
}
}
}
I get this error every time I launch a secondary picker.
The first picker works okay.
However when I switch pickers & scroll, I get the following:
Here is my entire code (written as a test of this problem):
import SwiftUI
struct ContentView: View {
#State private var selectedItem = 0
#State private var isMainPickerHidden = false
#State private var isSecondaryPickerHidden = true
var colors = ["Red", "Green", "Blue", "Tartan"]
var sizes = ["Tiny", "Small", "Medium", "Large", "Super Size"]
var body: some View {
ZStack {
Color.yellow.edgesIgnoringSafeArea(.all)
ZStack {
VStack {
Picker(selection: $selectedItem, label: Text("Please choose a color")) {
ForEach(colors.indices, id: \.self) {
Text(self.colors[$0])
}
}.hiddenConditionally(isHidden: isMainPickerHidden)
Text("You selected: \(colors[selectedItem])")
.hiddenConditionally(isHidden: isMainPickerHidden)
}
VStack {
Picker(selection: $selectedItem, label: Text("Please choose a size")) {
ForEach(sizes.indices, id: \.self) {
Text(self.sizes[$0])
}
}.hiddenConditionally(isHidden: isSecondaryPickerHidden)
Text("You selected: \(sizes[selectedItem])")
.hiddenConditionally(isHidden: isSecondaryPickerHidden)
Spacer()
Button(action: {
isSecondaryPickerHidden = !isSecondaryPickerHidden
isMainPickerHidden = !isMainPickerHidden
}) {
Text("Switch Pickers")
}.padding()
}
}
}
}
}
// =========================================================================================================
extension View {
func hiddenConditionally(isHidden: Bool) -> some View {
isHidden ? AnyView(hidden()) : AnyView(self)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
What is the correct syntax for the ForEach{} to avoid this problem?
This is because you use the same selectedItem for both pickers.
If in the second picker you select the last item (index 4) and then you switch to the first picker (max index = 3), then in this line:
Text("You selected: \(colors[selectedItem])")
you'll try accessing the index which is out of range.
To fix this you can use a separate #State variable for each picker:
struct ContentView: View {
#State private var selectedColorIndex = 0
#State private var selectedSizeIndex = 0
Picker(selection: $selectedColorIndex, label: Text("Please choose a color")) {
Picker(selection: $selectedSizeIndex, label: Text("Please choose a size")) {
In the swiftUI View below, there are two boolean #State variables (boolA and boolB) connected to two different pickers. Each picker has an .onReceive, with the following kind of publisher
[self.boolA].publisher.first()
(To be honest, I don't understand that line of code but it appears in several answers on S.O.)
In any case, whichever picker I change both .onReceive fire!
Questions: 1) Why does both onReceive fire? 2) How to avoid this?
struct ContentView: View {
#State private var boolA = false
#State private var boolB = false
var body: some View {
VStack{
Picker(selection: $boolA, label: Text("a? ")) {
Text("a is true").tag(true)
Text("a is false").tag(false)
}
.pickerStyle(SegmentedPickerStyle())
.onReceive([self.boolA].publisher.first()) { _ in
print("on receive on boolA")
}
Picker(selection: $boolB, label: Text("b? ")) {
Text("b is true").tag(true)
Text("b is false").tag(false)
}
.pickerStyle(SegmentedPickerStyle())
.onReceive([self.boolB].publisher.first()) { _ in
print("on receive on boolB")
}
Spacer()
}
}
}
You only need a single onRecieved in your View. Here's the code:
struct ContentView: View {
#State private var boolA = false
#State private var boolB = false
var body: some View {
VStack{
Picker(selection: $boolA, label: Text("a? ")) {
Text("a is true").tag(true)
Text("a is false").tag(false)
}
.pickerStyle(SegmentedPickerStyle())
Picker(selection: $boolB, label: Text("b? ")) {
Text("b is true").tag(true)
Text("b is false").tag(false)
}
.pickerStyle(SegmentedPickerStyle())
Spacer()
.onReceive([self.boolA, self.boolB].publisher.first()) { _ in
print("boolA:", self.boolA, "boolB:", self.boolB)
}
}
}
}
I am passing binding variable into other view:
struct PocketlistView: View {
#ObservedObject var pocket = Pocket()
#State var isSheetIsVisible = false
var body: some View {
NavigationView{
List{
ForEach(Array(pocket.pockets.enumerated()), id: \.element.id) { (index, pocketItem) in
VStack(alignment: .leading){
Text(pocketItem.name).font(.headline)
Text(pocketItem.type).font(.footnote)
}
.onTapGesture {
self.isSheetIsVisible.toggle()
}
.sheet(isPresented: self.$isSheetIsVisible){
PocketDetailsView(pocketItem: self.$pocket.pockets[index])
}
}
}
.listStyle(GroupedListStyle())
.navigationBarTitle("Pockets")
}
}
}
the other view is:
struct PocketDetailsView: View {
#Binding var pocketItem: PocketItem
var body: some View {
Text("\(pocketItem.name)")
}
}
Why I see the first item when i open sheet for second or third row?
When I use NavigationLink instead of the .sheet it works perfect
You activate all sheets at once, try the following approach (I cannot test your code, but the idea should be clear)
struct PocketlistView: View {
#ObservedObject var pocket = Pocket()
#State var selectedItem: PocketItem? = nil
var body: some View {
NavigationView{
List{
ForEach(Array(pocket.pockets.enumerated()), id: \.element.id) { (index, pocketItem) in
VStack(alignment: .leading){
Text(pocketItem.name).font(.headline)
Text(pocketItem.type).font(.footnote)
}
.onTapGesture {
self.selectedItem = pocketItem
}
}
}
.listStyle(GroupedListStyle())
.navigationBarTitle("Pockets")
.sheet(item: self.$selectedPocket) { item in
PocketDetailsView(pocketItem:
self.$pocket.pockets[self.pocket.pockets.firstIndex(of: item)!])
}
}
}
}
I have noticed that SwiftUI completely refresh view when adding sheetmodifier.
Let's say I have View that displays random number. I expect that this value would be independent and not connected to the sheet logic (not changing every time I open/close sheet), but every time sheet presented/dismissed Text is changing.
Is it supposed to work so?
Am I wrong that main point of #Sateis to update only connected Views but not all stack?
How can I prevent my View from refreshing itself when presenting a modal?
struct ContentView: View {
#State var active = false
var body: some View {
VStack {
Text("Random text: \(Int.random(in: 0...100))")
Button(action: { self.active.toggle() }) {
Text("Show pop up")
}
}
.sheet(isPresented: $active) {
Text("POP UP")
}
}
}
P.S. ContentView calls onAppear()/onDisappear() and init() only ones.
It needs to make separated condition-independent view to achieve behavior as you wish, like below
struct RandomView: View {
var body: some View {
Text("Random text: \(Int.random(in: 0...100))")
}
}
struct ContentView: View {
#State var active = false
var body: some View {
VStack {
RandomView()
Button(action: { self.active.toggle() }) {
Text("Show pop up")
}
}
.sheet(isPresented: $active) {
Text("POP UP")
}
}
}
In this case RandomView is not rebuilt because is not dependent on active state.
Asperi sad :
View is struct, value type, if any part of it changed then entire
value changed
He is absolutely right! But for that we have state properties. When the view is recreated, the value of state doesn't change.
This should work, as you expected
struct ContentView: View {
#State var active = false
#State var number = Int.random(in: 0 ... 100)
var body: some View {
VStack {
Text("Random text: \(number)")
Button(action: { self.active.toggle() }) {
Text("Show pop up")
}
}
.sheet(isPresented: $active) {
Text("POP UP")
}
}
}
What is the advantage? For simple things, the state / binding is the best solution, without any doubt.
import SwiftUI
struct SheetView: View {
#Binding var randomnumber: Int
var body: some View {
Button(action: {
self.randomnumber = Int.random(in: 0 ... 100)
}) {
Text("Generate new random number")
}
}
}
struct ContentView: View {
#State var active = false
#State var number = Int.random(in: 0 ... 100)
var body: some View {
VStack {
Text("Random text: \(number)")
Button(action: { self.active.toggle() }) {
Text("Show pop up")
}
}
.sheet(isPresented: $active) {
SheetView(randomnumber: self.$number)
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
Now you can dismiss the sheet with or without generating new random number. No external model is required ...