I have found this question while scouring for some info for my project. It was unanswered, but I used it as an answer to my problem after a little fix '^^
The question:
how to change from default "2 cups" to 1 cup. ? My coffeAmmount is 1 so as I understand $0 should also be 1 in Text view. But its showing default as 2. Can someone explain ?
thanks.!!
The code:
import SwiftUI
struct ContentView: View {
#State private var coffeAmmount = 1
var body: some View {
Section(header: Text("Daily coffe intake")
.font(.headline)){
Picker("How many cups", selection: $coffeAmmount){
ForEach(1..<21){
Text($0 > 1 ? "\($0) cups" : "\($0) cup")
}
}
}
}
}
The original topic:
https://www.hackingwithswift.com/forums/100-days-of-swiftui/betterrest-day-28-challenge-2-how-to-create-a-simple-integer-picker/587
The other fix would be to make it an array, and not a range. This may be a bit more intuitive for some as your are always dealing with the numbers you actually set in the ForEach like this:
struct CoffeeView: View {
#State private var coffeAmmount = 1
var body: some View {
Picker("How many cups", selection: $coffeAmmount){
// make this an Array and the value matches
ForEach(Array(1..<21), id: \.self){ cup in
Text(cup > 1 ? "\(cup) cups" : "\(cup) cup")
}
}
}
}
You just have to set
coffeAmmount
to 0:
#State private var coffeAmmount = 0
SwiftUI treats this variable as a pointer to the place in range you created with use of ForEach.
So the ForEach range is (1, 2, 3, ..., 20) but their indexes are 0 for 1; 1 for 2 etc. Swift, as many of the programming languages, starts counting the indexes and other stuff from 0 not from 1 by default.
By setting coffeAmmount to 0 you actually show Xcode that you want the value from the index (place in range you created) "branded" 0 which value is 1 :)
Hope that helps people with the similar problem, since the question was asked 2 years ago.
Related
I am trying to create a LazyVGrid based on user selection in another view. As follows, the peoplelist and selectedpersonID are coming from other view.
I understand that I cannot use the "selectedpersons" during initializing of this view. I looked here(Cannot use instance member 'service' within property initializer; property initializers run before 'self' is available) to use onAppear() of the LazyVGrid.
It goes well during compiling and works ok if you select 1 person.
Once I selected 2 persons, I got a Fatal error that Index out of range at row.
struct Someview: View {
#ObservedObject var peoplelist : PersonList
let selectedpersonID : Set<UUID>?
#State private var days : [String] = Array(repeating: "0", count: selectedpersons.count * 5) //got first error here, during compiling
var body: some View {
VStack{
LazyVGrid(columns: columns) {
Text("")
ForEach(1..<6) { i in
Text("\(i)").bold()
}
ForEach(0..< selectedpersons.count , id: \.self) { row in
Text(selectedpersons[row].Name)
ForEach(0..<5) { col in
TextField("", text: $days[row * 5 + col])
}
}
}
.onAppear(){
days = Array(repeating: "0", count: selectedpersons.count * 5)}//no problem during compiling, but will have error when more than 1 person are selected.
.padding()
}
}
var selectedpersons: [Persons] {
return peoplelist.persons.filter {selectedpersonID!.contains($0.id)}
}
}
It seems to me that this OnAppear() is still slower than the content inside the LazyVGrid? So, the days is not changed quick enough for building the content insider the LazyVGrid?
Or did I make an error of the index in the array of days?
It's crashing because ForEach isn't a for loop its a View that needs to be supplied Identifiable data. If you're using indices, id: \self or data[index] then something has gone wrong. There are examples of how to use it correctly in the documentation.
Also onAppear is for performing a side-effect action when the UIView that SwiftUI manages appears, it isn't the correct place to set view data, the data should be already in the correct place when the View struct is init. Making custom Views is a good way to solve this.
As the title suggests I'm getting an error in the below code (related to the loop when trying to build.
struct ContentView: View {
var testImages = ["Image1", "Image2", "Image3"].shuffled()
var body: some View {
VStack{
ForEach(0...2) { number in
Image(self.testImages[number])
}
}
}
}
Any help would be much appreciated.
0...2 is a type of ClosedRange, but ForEach only works with Range types.
Try changing the loop to use the ..< range syntax:
ForEach(0..<3) { number in
Image(self.testImages[number])
}
use the code below, this will count the number of elements in the array, at least you won't need to modify the number each time you add or remove elements in your array
ForEach(0..<Int(testImages.count), id:\.self) { number in
Image(self.testImages[number])
}
This question already has answers here:
SwiftUI #State var initialization issue
(8 answers)
Closed 1 year ago.
Navigating from view A to view B, i m passing a var show . View A isn t visible anymore .
I need to have a #State var stateShow whose initial value is the same as value show passed to B from A .
How to do it without using onAppear ? Thanx
struct B : View {
public var show:Bool
#State private stateShow : Bool
init (_ show : Bool){
self.show = show
}
}
init (_ show : Bool){
self.show = show
_stateShow = State(initialValue: show)
}
Answer credited to vadian ,another similar question was asked with a similar answer but slightly different conditions :
Why running this code shows "Fatal error: Index out of range"?
import SwiftUI
struct MyData {
var numbers = [Int](repeating: 0, count: 5)
}
#main
struct TrySwiftApp: App {
#State var myData = MyData()
var body: some Scene {
WindowGroup {
ChildView(myData: myData)
.frame(width: 100, height: 100)
.onAppear {
myData.numbers.removeFirst() // change myData
}
}
}
}
struct ChildView: View {
let myData: MyData // a constant
var body: some View {
ForEach(myData.numbers.indices) {
Text("\(myData.numbers[$0])") // Thread 1: Fatal error: Index out of range
}
}
}
After checking other questions,
I know I can fix it by following ways
// fix 1: add id
ForEach(myData.numbers.indices, id: \.self) {
//...
}
or
// Edited:
//
// This is not a fix, see George's reply
//
// fix 2: make ChildView conforms to Equatable
struct ChildView: View, Equatable {
static func == (lhs: ChildView, rhs: ChildView) -> Bool {
rhs.myData.numbers == rhs.myData.numbers
}
...
My Questions:
How a constant value (defined by let) got out of sync?
What ForEach really did?
Let me give you a simple example to show you what happened:
struct ContentView: View {
#State private var lowerBound: Int = 0
var body: some View {
ForEach(lowerBound..<11) { index in
Text(String(describing: index))
}
Button("update") { lowerBound = 5 }.padding()
}
}
if you look at the upper code you would see that I am initializing a ForEach JUST with a Range like this: lowerBound..<11 which it means this 0..<11, when you do this you are telling SwiftUI, hey this is my range and it will not change! It is a constant Range! and SwiftUI says ok! if you are not going update upper or lower bound you can use ForEach without showing or given id! But if you see my code again! I am updating lowerBound of ForEach and with this action I am breaking my agreement about constant Range! So SwiftUI comes and tell us if you are going update my ForEach range in count or any thing then you have to use an id then you can update the given range! And the reason is because if we have 2 same item with same value, SwiftUI would have issue to know which one you say! with using an id we are solving the identification issue for SwiftUI! About id you can use it like this: id:\.self or like this id:\.customID if your struct conform to Hash-able protocol, or in last case you can stop using id if you confrom your struct to identifiable protocol! then ForEach would magically sink itself with that.
Now see the edited code, it will build and run because we solved the issue of identification:
struct ContentView: View {
#State private var lowerBound: Int = 0
var body: some View {
ForEach(lowerBound..<11, id:\.self) { index in
Text(String(describing: index))
}
Button("update") { lowerBound = 5 }.padding()
}
}
Things go wrong when you do myData.numbers.removeFirst(), because now myData.numbers.indices has changed and so the range in the ForEach showing Text causes problems.
You should see the following warning (at least I do in Xcode 13b5) hinting this could cause issues:
Non-constant range: not an integer range
The reason it is not constant is because MyData's numbers property is a var, not let, meaning it can change / not constant - and you do change this. However the warning only shows because you aren't directly using a range literal in the ForEach initializer, so it assumes it's not constant because it doesn't know.
As you say, you have some fixes. Solution 1 where you provide id: \.self works because now it uses a different initializer. Definition for the initializer you are using:
#available(iOS 13.0, macOS 10.15, tvOS 13.0, watchOS 6.0, *)
extension ForEach where Data == Range<Int>, ID == Int, Content : View {
/// Creates an instance that computes views on demand over a given constant
/// range.
///
/// The instance only reads the initial value of the provided `data` and
/// doesn't need to identify views across updates. To compute views on
/// demand over a dynamic range, use ``ForEach/init(_:id:content:)``.
///
/// - Parameters:
/// - data: A constant range.
/// - content: The view builder that creates views dynamically.
public init(_ data: Range<Int>, #ViewBuilder content: #escaping (Int) -> Content)
}
Stating:
The instance only reads the initial value of the provided data and doesn't need to identify views across updates. To compute views on demand over a dynamic range, use ForEach/init(_:id:content:).
So that's why your solution 1 worked. You switched to the initializer which didn't assume the data was constant and would never change.
Your solution 2 isn't really a "solution". It just doesn't update the view at all, because myData.numbers changes so early that it is always equal, so the view never updates. You can see the view still has 5 lines of Text, rather than 4.
If you still have issues with accessing the elements in this ForEach and get out-of-bounds errors, this answer may help.
I'm trying to create a simple app that keeps count of how buttons in a list of clothing items have received more than 5 taps.
I've tried using the code below, but keep getting the error "Cannot convert value of type 'ContentView.clothing' to expected argument type 'Int'" in the line if clothes[i].taps >= 5.
I feel like somehow this might be related to the fact that I've tried to pass a whole struct as a parameter of the func. Perhaps I'm not meant to do this?
Any guidance much appreciated!
import SwiftUI
struct ContentView: View {
struct clothing {
var type: String
var taps: Int
}
#State var currentClothes = [
clothing(type: "tshirt", taps: 0),
clothing(type: "dress", taps: 0)
]
var body: some View {
NavigationView{
List{
ForEach(0..<currentClothes.count) { i in
Button("\(currentClothes[i].type)") {
self.currentClothes[i].taps += 1
print(currentClothes)
}
}
}
Text("\(tapCount(clothes: currentClothes))")
}
}
func tapCount(clothes: [clothing]) -> Int {
var total = 0
for i in clothes {
if clothes[i].taps >= 5
{total += 1}
}
return total
}
}
It should be
for i in clothes {
if i.taps >= 5
{total += 1}
}
not
for i in clothes {
if clothes[i].taps >= 5
{total += 1}
}
because you are looping over clothes, not clothes.count or something. i is a clothing, not an Int.
As a side note, try to keep your classes and structs Uppercased. clothing would be better off as Clothing.