I have a Picker within a Form but I want to show the selected value of the Picker only in another TextField within this Form and not in the Picker.
Is there a possibility to hide the selected value in a Picker?
You can't do this with a Picker but you could use NavigationLink as a work-around:
struct ContentView: View {
#State private var input = ""
#State private var active = false
var body: some View {
NavigationView {
Form {
NavigationLink("Select", isActive: $active) {
List {
Button("Item 1") {
input = "Item 1"
active = false
}
Button("Item 2") {
input = "Item 2"
active = false
}
Button("Item 3") {
input = "Item 3"
active = false
}
}
}
TextField("", text: $input)
}
}
}
}
Related
In the view shown below there is a simple list of 3 items. When the user selects an item in the list a sheet is presented showing the name of the item selected. However, when I run it, the first time I select an item it shows "item was null". If I select another item in the list it works perfectly. If I go back and select the first item again, it now works.
Can someone tell me why the selectedItem variable is null the first time a button is clicked?
struct TestView: View {
#State private var showSheet = false
#State private var selectedItem: String?
var body: some View {
List {
Button(action: {
selectedItem = "Item 1"
showSheet = true
}, label: { Text("Item 1") })
Button(action: {
selectedItem = "Item 2"
showSheet = true
}, label: { Text("Item 2") })
Button(action: {
selectedItem = "Item 3"
showSheet = true
}, label: { Text("Item 3") })
}
.sheet(isPresented: $showSheet) {
Text(selectedItem ?? "item was null")
}
}
}
As discussed in the comments, you're going to need to use .sheet(item:). The reason for this is that the common .sheet(isPresented:) is created before the button is tapped.
When using .sheet(item:) the string needs to be identifiable, but you can achieve that with a simple extension.
And now you also don't need the showSheet bool, because the sheet is now bound to selectedItem. Keep in mind that this means that selectedItem is set to nil when the sheet is dismissed.
An example of what this solution could look like for your code is as follows:
struct TestView: View {
#State private var selectedItem: String?
var body: some View {
List {
Button(action: {
selectedItem = "Item 1"
}, label: { Text("Item 1") })
Button(action: {
selectedItem = "Item 2"
}, label: { Text("Item 2") })
Button(action: {
selectedItem = "Item 3"
}, label: { Text("Item 3") })
}
.sheet(item: $selectedItem, content: { item in
Text(item)
})
}
}
extension String: Identifiable {
public var id: String { return self }
}
struct ContentView: View {
#State var showModal = false
#State var text = "Empty"
var body: some View {
Button("show text") {
text = "Filled"
showModal = true
}
.sheet(isPresented: $showModal) {
VStack {
Text(text)
Button("print text") {
print(text)
}
}
}
}
}
I thought that when the "show text" button was tapped, the value of text would be set to "Filled" and showModal would be set to true, so that the screen specified in sheet would be displayed and the word "Filled" would be shown on that screen.
I thought it would show "Filled", but it actually showed "Empty".
Furthermore, when I printed the text using the print text button, the console displayed "Filled".
Why does it work like this?
What am I missing to display the value I set when I tap the button on the destination screen?
using Xcode12.4, Xcode12.5
Add the code for the new pattern.
struct ContentView: View {
#State var number = 0
#State var showModal = false
var body: some View {
VStack {
Button("set number 1") {
number = 1
showModal = true
print("set number = \(number)")
}
Button("set number 2") {
number = 2
showModal = true
print("set number = \(number)")
}
Button("add number") {
number += 1
showModal = true
print("add number = \(number)")
}
}
.sheet(isPresented: $showModal) {
VStack {
let _ = print("number = \(number)")
Text("\(number)")
}
}
}
}
In the above code, when I first tap "set number 1" or "set number 2", the destination screen shows "0". No matter how many times you tap the same button, "0" will be displayed.
However, if you tap "set number 2" after tapping "set number 1", it will work correctly and display "2". If you continue to tap "set number 1", "1" will be displayed and the app will work correctly.
When you tap "add number" for the first time after the app is launched, "0" will still be displayed, but if you tap "add number" again, "2" will be displayed and the app will count up correctly.
This shows that the rendering of the destination screen can be started even when the #State variable is updated, but only when the #State variable is referenced first in the destination screen, it does not seem to be referenced properly.
Can anyone explain why it behaves this way?
Or does this look like a bug in SwiftUI?
Since iOS 14, there are a couple of main ways of presenting a Sheet.
Firstly, for your example, you need to create a separate View and pass your property to a Binding, which will then be correctly updated when the Sheet is presented.
// ContentView
Button { ... }
.sheet(isPresented: $showModal) {
SheetView(text: $text)
}
struct SheetView: View {
#Binding var text: String
var body: some View {
VStack {
Text(text)
Button("print text") {
print(text)
}
}
}
}
The other way of doing it is by using an Optional identifiable object, and when that object has a value the sheet will be presented. Doing that, you do not need to separately manage the state of whether the sheet is showing.
struct Item: Identifiable {
var id = UUID()
var text: String
}
struct ContentView: View {
#State var item: Item? = nil
var body: some View {
Button("show text") {
item = Item(text: "Filled")
}
.sheet(item: $item, content: { item in
VStack {
Text(item.text)
Button("print text") {
print(item.text)
}
}
})
}
}
By adding the following code, I was able to display the word "Filled" in the destination screen.
Declare the updateDetector as a #State variable.
Update the updateDetector onAppear of the View in the sheet.
Reference the updateDetector somewhere in the View in the sheet.
struct ContentView: View {
#State var showModal = false
#State var updateDetector = false
#State var text = "Empty"
var body: some View {
Button("show text") {
text = "Filled"
print("set text to \(text)")
showModal = true
}
.sheet(isPresented: $showModal) {
let _ = print("render text = \(text)")
VStack {
Text(text)
// use EmptyView to access updateDetector
if updateDetector {
EmptyView()
}
}
.onAppear {
// update updateDetector
print("toggle updateDetector")
updateDetector.toggle()
}
}
}
}
Then, after rendering the initial value at the time of preloading, the process of updating the updateDetector onAppear will work, the View will be rendered again, and the updated value of the #State variable will be displayed.
When you tap the "show text" button in the above code, the following will be displayed in the console and "Filled" will be shown on the screen.
set text to Filled
render text = Empty
toggle updateDetector
render text = Filled
I'm still not convinced why I can't get the updated value of the #State variable in the first preloaded sheet. So I will report this to Apple via the Feedback Assistant.
For some reason I don't understand, when I add/remove items from a #State var in MainView, the OutterViews are not being updated properly.
What I am trying to achieve is that the user can only "flag" (select) one item at a time. For instance, when I click on "item #1" it will be flagged. If I click on another item then "item #1" will not be flagged anymore but only the new item I just clicked.
Currently, my code shows all items as if they were flagged even when they are not anymore. The following code has the minimum structure and functionality I'm implementing for MainView, OutterView, and InnerView.
I've tried using State vars instead of the computed property in OutterView, but it doesn't work. Also, I tried using a var instead of the computed property in OutterViewand initialized it in init() but also doesn't work.
Hope you can help me to find what I am doing wrong.
Thanks!
struct MainView: View {
#State var flagged: [String] = []
var data: [String] = ["item #1", "item #2", "item #3", "item #4", "item #5"]
var body: some View {
VStack(spacing: 50) {
VStack {
ForEach(data, id:\.self) { text in
OutterView(text: text, flag: flagged.contains(text)) { (flag: Bool) in
if flag {
flagged = [text]
} else {
if let index = flagged.firstIndex(of: text) {
flagged.remove(at: index)
}
}
}
}
}
Text("Flagged: \(flagged.description)")
Button(action: {
flagged = []
}, label: {
Text("Reset flagged")
})
}
}
}
struct OutterView: View {
#State private var flag: Bool
private let text: String
private var color: Color { flag ? Color.green : Color.gray }
private var update: (Bool)->Void
var body: some View {
InnerView(color: color, text: text)
.onTapGesture {
flag.toggle()
update(flag)
}
}
init(text: String, flag: Bool = false, update: #escaping (Bool)->Void) {
self.text = text
self.update = update
_flag = State(initialValue: flag)
}
}
struct InnerView: View {
let color: Color
let text: String
var body: some View {
Text(text)
.padding()
.background(
Capsule()
.fill(color))
}
}
Here's a simple version that does what you're looking for (explained below):
struct Item : Identifiable {
var id = UUID()
var flagged = false
var title : String
}
class StateManager : ObservableObject {
#Published var items = [Item(title: "Item #1"),Item(title: "Item #2"),Item(title: "Item #3"),Item(title: "Item #4"),Item(title: "Item #5")]
func singularBinding(forIndex index: Int) -> Binding<Bool> {
Binding<Bool> { () -> Bool in
self.items[index].flagged
} set: { (newValue) in
self.items = self.items.enumerated().map { itemIndex, item in
var itemCopy = item
if index == itemIndex {
itemCopy.flagged = newValue
} else {
//not the same index
if newValue {
itemCopy.flagged = false
}
}
return itemCopy
}
}
}
func reset() {
items = items.map { item in
var itemCopy = item
itemCopy.flagged = false
return itemCopy
}
}
}
struct MainView: View {
#ObservedObject var stateManager = StateManager()
var body: some View {
VStack(spacing: 50) {
VStack {
ForEach(Array(stateManager.items.enumerated()), id:\.1.id) { (index,item) in
OutterView(text: item.title, flag: stateManager.singularBinding(forIndex: index))
}
}
Text("Flagged: \(stateManager.items.filter({ $0.flagged }).map({$0.title}).description)")
Button(action: {
stateManager.reset()
}, label: {
Text("Reset flagged")
})
}
}
}
struct OutterView: View {
var text: String
#Binding var flag: Bool
private var color: Color { flag ? Color.green : Color.gray }
var body: some View {
InnerView(color: color, text: text)
.onTapGesture {
flag.toggle()
}
}
}
struct InnerView: View {
let color: Color
let text: String
var body: some View {
Text(text)
.padding()
.background(
Capsule()
.fill(color))
}
}
What's happening:
There's a Item that has an ID for each item, the flagged state of that item, and the title
StateManager keeps an array of those items. It also has a custom binding for each index of the array. For the getter, it just returns the state of the model at that index. For the setter, it makes a new copy of the item array. Any time a checkbox is set, it unchecks all of the other boxes.
The ForEach now gets an enumeration of the items. This could be done without enumeration, but it was easy to write the custom binding by index like this. You could also filter by ID instead of index. Note that because of the enumeration, it's using .1.id for the id parameter -- .1 is the item while .0 is the index.
Inside the ForEach, the custom binding from before is created and passed to the subview
In the subview, instead of using #State, #Binding is used (this is what the custom Binding is passed to)
Using this strategy of an ObservableObject that contains all of your state and passes it on via #Published properties and #Bindings makes organizing your data a lot easier. It also avoids having to pass closures back and forth like you were doing initially with your update function. This ends up being a pretty idiomatic way of doing things in SwiftUI.
Scenario:
I have a simple picker within a form.
I select a picker item (with chevron) from the form row.
I choose an item (row) from a list of items in the result panel.
The result panel slides away to reveal the original panel.
I am NOT able to repeat this procedure.
Here's my code:
class ChosenView: ObservableObject {
static let choices = ["Modal", "PopOver", "Circle", "CircleImage", "Scroll", "Segment", "Tab", "Multi-Line"]
#Published
var type = 0
}
struct ContentView: View {
#ObservedObject var chosenView = ChosenView()
#State private var isPresented = false
var body: some View {
VStack {
NavigationView {
Form {
Picker(selection: $chosenView.type, label: Text("The Panels")) {
ForEach(0..<ChosenView.choices.count) {
Text(ChosenView.choices[$0]).tag($0)
}
}
}.navigationBarTitle(Text("Available Views"))
.actionSheet(isPresented: $isPresented, content: {
ActionSheet(title: Text("Hello"))
})
}
Section {
Button(action: launchView) {
Text("Select: \(ChosenView.choices[chosenView.type])")
}
}
Spacer()
}
}
private func launchView() {
isPresented = true
}
}
What am I missing?
Why can't I repeat picker selection rather than having to reboot?
Within my List I have some static items. I want to dynamically hide/show an item when the user taps another list item, i.e. I want to change a #State property when the user taps a specific list item.
How do I do that?
struct EditTransactionView : View {
#State var date = Date()
#State private var showingDateSelector = false // How do I change this with a tap on the date list item?
var body: some View {
NavigationView {
List {
DateView(date: $date)
if showingDateSelector {
DatePicker(
$date,
maximumDate: Date(),
displayedComponents: .date )
}
}
}
}
}
Something like this :
struct EditTransactionView : View {
#State var date = Date()
#State private var showingDateSelector = false // How do I change this with a tap on the date list item?
var body: some View {
NavigationView {
List {
Button(action: { self.showingDateSelector.toggle() }) {
DateView(date: $date)
}
if showingDateSelector {
DatePicker(
$date,
maximumDate: Date(),
displayedComponents: .date )
}
}
}
}
}