I'm working on MacOS and I try to make NumberField — something like TextField, but for numbers. In rather big tree of views at the top I had:
...
VStack {
ForEach(instances.indices, id:\.self) {index in
TextField("",
text: Binding(
get: {"\(String(format: "%.1f", instances[index].values[valueIndex]))"},
set: {setValueForInstance(index, valueIndex, $0)})
)
}
}
...
And it worked well, but not nice:
✔︎ when I changed value, all View structure was redrawn – good
✔︎ values was updated if they were changed by another part of Views structure – good
✖︎ it was updated after each keypresses, which was annoying, when I tried to input 1.2, just after pressing 1 view was updated to 1.0. Possible to input every number but inconvenient – bad
So, I tried to build NumberField.
var format = "%.1f"
struct NumberField : View {
#Binding var number: Double {
didSet {
stringNumber = String(format: format, number)
}
}
#State var stringNumber: String
var body: some View {
TextField("" , text: $stringNumber, onCommit: {
print ("Commiting")
if let v = Double(stringNumber) {
number = v
} else {
stringNumber = String(format:format, number)
}
print ("\(stringNumber) , \(number)" )
})
}
init (number: Binding<Double>) {
self._number = number
self._stringNumber = State(wrappedValue: String(format:format, number.wrappedValue))
}
}
And It's called from the same place as before:
...
VStack {
ForEach(instances.indices, id:\.self) {index in
NumberField($instances[index].values[valueIndex])
}
}
...
But in this case it never updates NumberField View if values was changed by another part of View. Whats's wrong? Where is a trick?
Related
I am currently working on an app with class schedule. I need to implement a swipable week view just like in Apple's "Calendar" app. There is no built-in solution for this in SwiftUI (Maybe I didn't find it), so I used SwiftUIPager library. It kinda works, but I have to provide it an array of elements. Then Pager use this elements to create pages. This does not suit me, so I decided to dynamically add elements of the array when I approach its border.
struct WeekObserverView: View {
let vm: WeekObserverViewModel = WeekObserverViewModel()
let OnDayChanged: (Date)->Any
#State private var selectedDay = Date()
#State private var currentPage = Page.withIndex(2)
#State private var data = Array(-2..<3)
#State private var disableButtons = false
var body: some View {
VStack(spacing: 0){
VStack(alignment: .center, spacing: 0){
Pager(page: currentPage,
data: data,
id: \.self) {
self.generateWeekView($0)
}
.singlePagination(ratio: 0.5, sensitivity: .high)
.onPageWillChange({ (page) in
withAnimation {
//Moving forward or backward a week
selectedDay = selectedDay + TimeInterval(604800) * Double((page - currentPage.index))
}
_ = OnDayChanged(selectedDay)
})
.onPageChanged({
page in
//Adding new weeks when we approach the boundaries of the array
if page == 1 {
let newData = (1...5).map { data.first! - $0 }.reversed()
withAnimation {
currentPage.update(.move(increment: newData.count))
data.insert(contentsOf: newData, at: 0)
}
} else if page == self.data.count - 2 {
guard let last = self.data.last else { return }
let newData = (1...5).map { last + $0 }
withAnimation {
data.append(contentsOf: newData)
}
}
disableButtons = false
})
.onDraggingBegan({
disableButtons = true
})
.pagingPriority(.simultaneous)
.frame(height: 48)
Capsule()
.frame(width: 32, height: 6)
.foregroundColor(Color("TransparetPurple"))
.padding(4)
}
.frame(maxWidth: .infinity)
.background(Color("AccentBlue"))
//Spacer()
}
}
The problem is when I adding element to the front of array Pager loses current page and goes to the next page on the left.
I tried to add one extra page to the index, but it didn't work
currentPage.update(.move(increment: newData.count + 1))
Maybe there is a more simple solution without providing an array? I want Pager to just give me the offset from first loaded page.
I looked into this and checked an example called InfiniteExampleView included in the git project for SwiftUIPager.
I noticed how they are able to add items to the array dynamically both in front of the current items and behind them.
I can't test your code completely since there are some missing parts to make it run the way you run it, but it seems when they insert in front of current items they update the page index as well and I don't see you do that in your code.
This is the code from the example:
if page == 1 {
let newData = (1...5).map { data1.first! - $0 }.reversed()
withAnimation {
page1.index += newData.count //<-- this line
data1.insert(contentsOf: newData, at: 0)
isPresented.toggle()
}
}
this is your code under the withAnimation part of if statement page==1:
currentPage.update(.move(increment: newData.count))
data.insert(contentsOf: newData, at: 0)
So maybe adding a line to change the index helps fix this. If not, please provide a more complete example to make it possible to debug it more easily.
I've learning SwiftUI for a week, recently I found a confusing issue with it.
#State private var checkAmount = 0.0
var body: some View {
NavigationView {
Form {
Section {
TextField("Amount", value: $checkAmount, format: .currency(code: Locale.current.currency?.identifier ?? "USD"))
.keyboardType(.decimalPad)
}
Section{
Text(checkAmount, format:.currency(code: Locale.current.currency?.identifier ?? "USD"))
}
}
}
}
I use TextFile to receive user's input and alter the value of checkAmount, and make the value shown in the section below. Here is my preview in xcode.
Preview
But when I type a random number and delete it all, this happend:
Still a digit here
It seems SwiftUI didn't delete it all, and still keep the last digit I deleted.
I guess maybe I should give it an default value when user's input is empty?
Some additional information maybe necessary: I'm using a M1 MacMini and XCode 14.1
Approach
For currency(code:) the value type is Decimal, so you have to use Optional Decimal
https://developer.apple.com/documentation/foundation/parseableformatstyle/3796617-currency
When the last digit is deleted it becomes nil
Use checkAmount ?? 0 in your TextField
Code
struct ContentView: View {
#State private var checkAmount = Decimal?(0.0) //Optional decimal
var body: some View {
NavigationView {
Form {
Section {
TextField("Amount", value: $checkAmount, format: .currency(code: Locale.current.currency?.identifier ?? "USD"))
.keyboardType(.decimalPad)
}
Section{
//Use ?? operator to display 0 when nil
Text(checkAmount ?? 0, format:.currency(code: Locale.current.currency?.identifier ?? "USD"))
}
}
.onChange(of: checkAmount) { newValue in
print("checkAmount = \(String(describing: newValue))")
}
}
}
}
I've defined a view in SwiftUI which takes an Int array and is supposed to display the elements of the array in a VStack such that every "full row" contains three elements of the array and then the last "row" contains the remainder of elements. When running the app on iOS16 I get "Fatal error: Can't remove first element from an empty collection" for the call let die = dice.removeFirst() (also when passing in a non-empty array of course). I've tried following the debugger but I don't understand the way it jumps around through the loops.
On iOS15 this code worked fine. In the actual program I don't display the array content as Text but I have images associated with each Int between 1 and 6 which I display. I replaced this with Text for simplicity's sake.
Thanks for any help!
struct DiceOnTableView: View {
let diceArray: [Int]
var body: some View {
let fullRows: Int = diceArray.count / 3
let diceInLastRow: Int = diceArray.count % 3
var dice: [Int] = diceArray
VStack {
ForEach(0..<fullRows, id: \.self) { row in
HStack {
ForEach(0..<3) { column in
let die = dice.removeFirst()
Text("\(die)")
}
}
}
HStack {
ForEach(0..<diceInLastRow, id: \.self) { column in
let die = dice.removeFirst()
Text("\(die)")
}
}
}
}
}
This does kind of work on iOS 15 (but strangely - the order of the dice is unexpected), and crashes on iOS 16. In general, you should not be using vars in SwiftUI view building code.
Your code can be modified to compute the index into the original diceArray from the row, fullRows, and column values:
struct DiceOnTableView: View {
let diceArray: [Int]
var body: some View {
let fullRows: Int = diceArray.count / 3
let diceInLastRow: Int = diceArray.count % 3
VStack {
ForEach(0..<fullRows, id: \.self) { row in
HStack {
ForEach(0..<3) { column in
Text("\(diceArray[row * 3 + column])")
}
}
}
HStack {
ForEach(0..<diceInLastRow, id: \.self) { column in
Text("\(diceArray[fullRows * 3 + column])")
}
}
}
}
}
The ForEach View will crash if you use it like a for loop with dynamic number of items. You need to supply it an array of item structs with ids, e.g. one that is Identifiable, e.g.
struct DiceItem: Identifable {
let id = UUID()
var number: Int
}
#State var diceItems: [DiceItem] = []
ForEach(diceItems) { diceItem in
And perhaps use a Grid instead of stacks.
In a swiftUI view that I'm writing, I need to use a ForEach, accessing each element of a list and its index. Most of the information I could find about this said to use .enumerated() as in ForEach(Array(values.enumerated()), id: \.offset) { index, value in }
However when I try to do that in my view:
/// A popover displaing a list of items.
struct ListPopover: View {
// MARK: Properties
/// The array of vales to display.
var values: [String]
/// Whether there are more values than the limit and they are concatenated.
var valuesConcatenated: Bool = false
/// A closure that is called when the button next to a row is pressed.
var action: ((_ index: Int) -> Void)?
/// The SF symbol on the button in each row.
var actionSymbolName: String?
// MARK: Initializers
init(values: [String], limit: Int = 10) {
if values.count > limit {
self.values = values.suffix(limit - 1) + ["\(values.count - (limit - 1)) more..."]
valuesConcatenated = true
} else {
self.values = values
}
}
// MARK: Body
var body: some View {
VStack {
ForEach(Array(values.enumerated()), id: \.offset) { index, value in
HStack {
if !(index == values.indices.last && valuesConcatenated) {
Text("\(index).")
.foregroundColor(.secondary)
}
Text(value)
Spacer()
if action != nil && !(index == values.indices.last && valuesConcatenated) {
Spacer()
Button {
action!(index)
} label: {
Image(systemName: actionSymbolName ?? "questionmark")
}
.frame(alignment: .trailing)
}
}
.if((values.count - index) % 2 == 0) { view in
view.background(
Color(.systemGray5)
.cornerRadius(5)
)
}
}
}
}
}
I get the error The compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions on the line var body: some View {
I've also noticed that this code causes some other problems like making the Xcode autocomplete extremely slow.
Any ideas how I might be able to solve this? It seems like a pretty simple view and I think I'm doing the ForEach how I should.
Thanks!
This is a very misleading error. What it really means is you screwed something up in your body, but the compiler can't figure out the error, so it throws it on the body itself. The easiest way to find it is to comment out portions of your body in matched braces until the error goes away. In your case the issue is with this:
.if((values.count - index) % 2 == 0) { view in
view.background(
Color(.systemGray5)
.cornerRadius(5)
)
}
I am not sure what you are attempting to do, but .if is not valid syntax and I am not sure what view is or where it is supposed to come from.
I am a novice at programming and exploring SwiftUI. I've been tackling a challenge for too long, and hoping that someone can guide me to the right direction!
I want a list of interlinked sliders (as in Interlinked Multiple Sliders in SwiftUI), but with the number of sliders that change dynamically, depending on actions taken by a user.
For example, a user can choose various items, and later on adjust the percentage variable with sliders (and where these percentages are interdependent as in the linked example).
class Items: ObservableObject {
#Published var components = [ItemComponent]()
func add(component: itemComponent){
components.append(component)
}
}
struct ItemComponent: Hashable, Equatable, Identifiable {
var id = UUID().uuidString
var name: String = ""
var percentage: Double
}
Conceptually, it seems I need to do two things to adapt the linked code:
generate an array of Binding with the number of elements equal to Items.Component.EndIndex and
assign each Binding to the percentage of each ItemComponent.
I am fumbling on both. For 1., I can easily manually create any number of variables, e.g.
#State var value1 = 100
#State var value2 = 100
#State var value3 = 100
let allBindings = [$value1, $value2, $value3]
but how do I generate them automatically?
For 2., I can use ForEach() to call the components, or Index, but not both together:
ForEach(Items.components){ component in
Text("\(component.name)")
Text("\(component.percentage)")
}
ForEach(Items.components.indices){ i in
synchronizedSlider(from: allBindings, index: i+1)
}
In broken code, what I want is something like:
ForEach(Items.component){component in
HStack{
Text("component.name")
Spacer()
synchronizedSlider(from: allBindings[$component.percentage], index: component.indexPosition)
}
where allBindings[$component.percentage] is a binding array comprised of each itemComponent's percentage, and the index is an itemComponent's index.
I am happy to share more code if relevant. Any help would be greatly appreciated!
To adapt the existing code you linked, if you're going to have a dynamic number of sliders, you'll definitely want your #State to be an array, rather than individual #State variables, which would have to be hard coded.
Once you have that, there are some minor syntax issues changing the synchronizedBinding functions to accept Binding<[ItemComponent]> rather than [Binding<Double>], but they are pretty minor. Luckily, the existing code is pretty robust outside of the initial hard-coded states, so there isn't any additional math to do with the calculations.
I'm using ItemComponent rather than just Double because your sample code included it and having a model with a unique id makes the ForEach code I'm using for the sliders easier to deal with, since it expects uniquely-identifiable items.
struct ItemComponent: Hashable, Equatable, Identifiable {
var id = UUID().uuidString
var name: String = ""
var percentage: Double
}
struct Sliders: View {
#State var values : [ItemComponent] = [.init(name: "First", percentage: 100.0),.init(name: "Second", percentage: 0.0),.init(name: "Third", percentage: 0.0),.init(name:"Fourth", percentage: 0.0),]
var body: some View {
VStack {
Button(action: {
// Manually setting the values does not change the values such
// that they sum to 100. Use separate algorithm for this
self.values[0].percentage = 40
self.values[1].percentage = 60
}) {
Text("Test")
}
Button(action: {
self.values.append(ItemComponent(percentage: 0.0))
}) {
Text("Add slider")
}
Divider()
ScrollView {
ForEach(Array(values.enumerated()),id: \.1.id) { (index,value) in
Text(value.name)
Text("\(value.percentage)")
synchronizedSlider(from: $values, index: index)
}
}
}.padding()
}
func synchronizedSlider(from bindings: Binding<[ItemComponent]>, index: Int) -> some View {
return Slider(value: synchronizedBinding(from: bindings, index: index),
in: 0...100)
}
func synchronizedBinding(from bindings: Binding<[ItemComponent]>, index: Int) -> Binding<Double> {
return Binding(get: {
return bindings[index].wrappedValue.percentage
}, set: { newValue in
let sum = bindings.wrappedValue.indices.lazy.filter{ $0 != index }.map{ bindings[$0].wrappedValue.percentage }.reduce(0.0, +)
// Use the 'sum' below if you initially provide values which sum to 100
// and if you do not set the state in code (e.g. click the button)
//let sum = 100.0 - bindings[index].wrappedValue
let remaining = 100.0 - newValue
if sum != 0.0 {
for i in bindings.wrappedValue.indices {
if i != index {
bindings.wrappedValue[i].percentage = bindings.wrappedValue[i].percentage * remaining / sum
}
}
} else {
// handle 0 sum
let newOtherValue = remaining / Double(bindings.wrappedValue.count - 1)
for i in bindings.wrappedValue.indices {
if i != index {
bindings[i].wrappedValue.percentage = newOtherValue
}
}
}
bindings[index].wrappedValue.percentage = newValue
})
}
}