I am trying to adjust (reduce) the number of gridlines in my SwiftUI Chart.
I have the following code:
Chart() {
ForEach(self.viewModel.downloadHistory) { item in
LineMark(x: .value(String.empty, item.timestamp), y: .value(String.empty, item.value.floatValue))
.interpolationMethod(.stepCenter)
.foregroundStyle(Colors.download)
}
}
.chartXAxis(.hidden)
.frame(height: 64.0)
.gridColumnAlignment(.center)
.chartYAxis() {
AxisMarks() { value in
AxisGridLine(centered: true, stroke: StrokeStyle(dash: [4.0, 4.0]))
AxisValueLabel()
{
if let value = value.as(UInt64.self)
{
Text(DiskUtilities.toSpeedNoComma(value))
}
}
}
}
.padding()
This results in the following chart:
I like the design, however, I would like to:
Either reduce the number of gridlines.
Or only show the text at the 0%, 50% and 100% line. Is this possible?
Is either of those two options possible?
AxisMarks has various initializers that take parameters. The parameter you're interested in is values, which can be either AxisMarkValues or an array of some Plottable.
Try AxisMarkValues.automatic(desiredCount: 3).
Related
Im going through SwiftUI Controls in detail and writing example code for each init.
Theres two sets of inits for Picker.
One where you fill your list from an array etc. and what you pick goes into selection: binding.
But whats the second set of inits for?
Theyre under section 'Creating a picker for a collection'
I can fill the array from a collection using both these inits ok
But how do you get the selected item using the 2nd set of inits?
The selection: param is no longer a binding to an ivar but a Keypath to fill the list.
My question is how do I get the selected item using the 2nd set of inits.
See inits here:
https://developer.apple.com/documentation/swiftui/picker
For Picker there are 6 inits.
3 under 'Creating a picker'
these are ok. I fill the list from an array for example and store the selected item in a single result specified by the selection: param. It binds the result to one ivar.
There are also 3 inits under 'Creating a picker for a collection'
I got this to display the items from a collection
e.g. I modified the example code in the apple docs. The code in the docs doesn't compile so apple may be missing stuff.
import SwiftUI
enum Thickness: String, CaseIterable, Identifiable {
case thin
case regular
case thick
var id: String { rawValue }
}
//to use in ist must be Hashable
struct Border: Identifiable {
var color: Color
var thickness: Thickness
//Identifiable > Hashable > id > String
//var id: String { return "\(color.hashValue)" }
let id = UUID()
}
extension Color{
func colorName() -> String{
if self == Color.black{
return "black"
}
else if self == Color.red{
return "red"
}
else{
return "UNHANDLED"
}
}
}
struct CLCPickers_selection_FromCollection_View: View {
#State private var selectedObjectBorders = [
Border(color: .black, thickness: .thin),
Border(color: .red, thickness: .thick)
]
var body: some View {
VStack{
//------------------------------------------------------------------
Picker(
"Border Thickness",
sources: $selectedObjectBorders,
selection: \.thickness
) {
//------------------------------------------------------------------
//I added
//id: \.self
//Picker: the selection "thin" is invalid and does not have an associated tag, this will give undefined results.
//------------------------------------------------------------------
ForEach(Thickness.allCases,
id: \.self)
{ thickness in
Text(thickness.rawValue)
}
}
//------------------------------------------------------------------
Divider()
//------------------------------------------------------------------
//This just lists the colors in the arrays of Border
//QUESTION - how do I find out the currenly selected one?
//normaly selection: in the picker would be bound to the picked item
//but for this init selection: is a keypath
//selection: \.thickness
//so I can fill the Picker list using the keypath into the Border array.
//BUT HOW DO I FIND OUT THE CURRENTLY SELECTED ITEM?
//theres no binding?
//is there a .selectedItem property some where?
List(selectedObjectBorders) {
Text("\($0.color.colorName())")
}
}
}
}
Question was answered but poster removed it for some reason.
answer: this picker init which set the thinkness ivar of EVERY Border object in the collection.
To see the change I should have displayed the result to show thickness.rawvalue to see the change in every Border object
List(selectedObjectBorders) { border in
HStack{
Text("\(border.color.colorName())")
Text("\(border.thickness.rawValue)") //<<- will change when you select an item. All will match.
}
}
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])
}
So, I'm going through the SwiftUI documentation to get familiar. I was working on a grid sample app. It has the following code:
ForEach(allColors, id: \.description) { color in
Button {
selectedColor = color
} label: {
RoundedRectangle(cornerRadius: 4.0)
.aspectRatio(1.0, contentMode: ContentMode.fit)
.foregroundColor(color)
}
.buttonStyle(.plain)
}
It didn't occur to me first that ForEach is actually a struct, I thought it's a variation of the for in loop at first so I'm quite new at this. Then I checked the documentation.
When I read the documentation and some google articles for the ForEach struct, I didn't understand two points in the code:
So we are initializing the foreach struct with an array of colors. For the the ID why did they use .\description instead of .self?
Second is using color in. Since foreach is a struct and the paranthesis is the initializtion parameters this looks like the return type of a closure but why would we return individual colors to foreach? I thought the return is a collection of views or controls like button and label. This is like var anInteger: Int = 1 for example. What type does ForEach accept as a result of the closure? Or am I reading this all wrong?
So we are initializing the foreach struct with an array of colors. For the the ID why did they use .\description instead of .self?
It depends on the type of allColors. What you should have in mind that id here is expected to be stable. The documentation states:
It’s important that the id of a data element doesn’t change unless you replace the data element with a new data element that has a new identity. If the id of a data element changes, the content view generated from that data element loses any current state and animations.
So for example if colors are reference types (which are identifiable) and you swap one object with an identical one (in terms of field values), the identity will change, whereas description wouldn't (for the purposes of this example - just assuming intentions of code I have no access to).
Edit: Also note that in this specific example allColors appears to be a list of Color, which is not identifiable. So that's the reason behind the custom id keyPath.
Regarding your second point, note that the trailing closure is also an initialization parameter. To see this clearly we could use the "non-sugared" version:
ForEach(allColors, id: \.description, content: { color in
Button {
selectedColor = color
} label: {
RoundedRectangle(cornerRadius: 4.0)
.aspectRatio(1.0, contentMode: ContentMode.fit)
.foregroundColor(color)
}
.buttonStyle(.plain)
})
where content is a closure (an anonymous function) that gets passed an element of the collection and returns some View.
So the idea is something like this: "Give me an collection of identifiable elements and I will call a function for each of these elements expecting from you to return me some View".
I hope that this makes (some) sense.
Additional remarks regarding some of the comments:
It appears to me that the main source of confusion is the closure itself. So let's try something else. Let's write the same code without a closure:
ForEach's init has this signature:
init(_ data: Data, id: KeyPath<Data.Element, ID>, content: #escaping (Data.Element) -> Content)
Now, the content translates to:
A function with one parameter of type Data.Element, which in our case is inferred from the data so it is a Color. The function's return type is Content which is a view builder that produces some View
so our final code, which is equivalent to the first one, could look like this:
struct MyView: View {
let allColors: [Color] = [.red, .green, .blue]
#State private var selectedColor: Color?
var body: some View {
List {
ForEach(allColors, id: \.description, content: colorView)
}
}
#ViewBuilder
func colorView(color: Color) -> some View {
Button {
selectedColor = color
} label: {
RoundedRectangle(cornerRadius: 4.0)
.aspectRatio(1.0, contentMode: ContentMode.fit)
.foregroundColor(color)
}
.buttonStyle(.plain)
}
}
I hope that this could help to clarify things a little bit better.
I am trying to change the swipeAction from "Paid" to "UnPaid" based on payment status and somehow seems to be failing. Error: "The compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions"
Appreciate any help
struct ContentView: View {
var data: [Data] = [data1, data2, data3, data4]
#State var swipeLabel = true
var body: some View {
let grouped = groupByDate(data)
List {
ForEach(Array(grouped.keys).sorted(by: >), id: \.self) { date in
let studentsDateWise = grouped[date]!
Section(header:Text(date, style: .date)) {
ForEach(studentsDateWise, id:\.self) { item in
HStack {
Text(item.name)
padding()
Text(item.date, style: .time)
if(item.paymentStatus == false) {
Image(systemName: "person.fill.questionmark")
.foregroundColor(Color.red)
} else {
Image(systemName: "banknote")
.foregroundColor(Color.green)
}
} // HStack ends here
.swipeActions() {
if(item.paymentStatus) {
Button("Paid"){}
} else {
Button("UnPaid"){}
}
}
} // ForEach ends here...
} // section ends here
} // ForEach ends here
} // List ends here
} // var ends here
}
The body func shouldn't do any grouping or sorting. You need to prepare your data first into properties and read from those in body, e.g. in an onAppear block. Also if your Data is a struct you can't use id: \.self you need to either specify a unique identifier property on the data id:\.myUniqueID or implement the Indentifiable protocol by either having an id property or an id getter that computes a unique identifier from other properties.
I would suggest separating all this code into small Views with a small body that only uses one or a two properties. Work from bottom up. Then eventually with one View works on an array of dates and another on an array of items that contains the small Views made earlier.
You should probably also learn that if and foreach in body are not like normal code, those are converted into special Views. Worth watching Apple's video Demystify SwiftUI to learn about structural identity.
I was wondering how can one get DragGesture Velocity?
I understand the formula works and how to manually get it but when I do so it is no where what Apple returns (at least some times its very different).
I have the following code snippet
struct SecondView: View {
#State private var lastValue: DragGesture.Value?
private var dragGesture: some Gesture {
DragGesture()
.onChanged { (value) in
self.lastValue = value
}
.onEnded { (value) in
if lastValue = self.lastValue {
let timeDiff = value.time.timeIntervalSince(lastValue.time)
print("Actual \(value)") // <- A
print("Calculated: \((value.translation.height - lastValue.translation.height)/timeDiff)") // <- B
}
}
var body: some View {
Color.red
.frame(width: 50, height: 50)
.gesture(self.dragGesture)
}
}
From above:
A will output something like Value(time: 2001-01-02 16:37:14 +0000, location: (250.0, -111.0), startLocation: (249.66665649414062, 71.0), velocity: SwiftUI._Velocity<__C.CGSize>(valuePerSecond: (163.23212105439427, 71.91841849340494)))
B will output something like Calculated: 287.6736739736197
Note from A I am looking at the 2nd value in valuePerSecond which is the y velocity.
Depending on how you drag, the results will be either different or the same. Apple provides the velocity as a property just like .startLocation and .endLocation but unfortunately there is no way for me to access it (at least none that I know) so I have to calculate it myself, theoretically my calculations are correct but they are very different from Apple. So what is the problem here?
This is another take on extracting the velocity from DragGesture.Value. It’s a bit more robust than parsing the debug description as suggested in the other answer but still has the potential to break.
import SwiftUI
extension DragGesture.Value {
/// The current drag velocity.
///
/// While the velocity value is contained in the value, it is not publicly available and we
/// have to apply tricks to retrieve it. The following code accesses the underlying value via
/// the `Mirror` type.
internal var velocity: CGSize {
let valueMirror = Mirror(reflecting: self)
for valueChild in valueMirror.children {
if valueChild.label == "velocity" {
let velocityMirror = Mirror(reflecting: valueChild.value)
for velocityChild in velocityMirror.children {
if velocityChild.label == "valuePerSecond" {
if let velocity = velocityChild.value as? CGSize {
return velocity
}
}
}
}
}
fatalError("Unable to retrieve velocity from \(Self.self)")
}
}
Just like this:
let sss = "\(value)"
//Intercept string
let start = sss.range(of: "valuePerSecond: (")
let end = sss.range(of: ")))")
let arr = String(sss[(start!.upperBound)..<(end!.lowerBound)]).components(separatedBy: ",")
print(Double(arr.first!)!)