I need to refresh SwiftUI View, when #propertyWrapper is passed into - swift

Question

I have an example struct:
public struct Axis: Hashable, CustomStringConvertible {
public var name: String
public var description: String {
return "Axis: \"\(name)\""
}
}
And property wrapper to make some operations on [Axis] struct.
#propertyWrapper
struct WrappedAxes {
var wrappedValue: [Axis] {
// This is just example, in real world it's much more complicated.
didSet {
for index in wrappedValue.indices {
var elems = Array(wrappedValue[index].name.split(separator: " "))
if elems.count>1 {
elems.removeLast()
}
let new = elems.reduce(into:"", {$0 += "\($1) "})
wrappedValue[index].name = new+("\(Date())")
} } } }
And I try to add, insert and remove Axes in SwiftUI View:
public struct ContentView: View {
#Binding var axes: [Axis]
public var body: some View {
VStack {
ForEach(axes.indices, id:\.self) {index in
HStack {
TextField("", text: $axes[index].name)
Button("Delete", action: {deleteAxis(index)})
Button("Insert", action: {insertAxis(index)})
}
}
Button("Add", action: addAxis)
}
}
var addAxis: () -> Void {
return {
axes.append(Axis(name: "New"))
print (axes)
}
}
var deleteAxis: (_:Int)->Void {
return {
if $0 < axes.count {
axes.remove(at: $0)
}
print (axes)
}
}
var insertAxis: (_:Int)->Void {
return {
if $0 < axes.count {
axes.insert(Axis(name: "Inserted"), at: $0)
}
print (axes)
}
}
public init (axes: Binding<[Axis]>) {
self._axes = axes
}
}
As far, as print (axes) shows changes are made, View never updates. I made very small App to test in which I call ContentView:
class AppDelegate: NSObject, NSApplicationDelegate {
var window: NSWindow!
#WrappedAxes var axes = [Axis(name: "FirstOne")]
func applicationDidFinishLaunching(_ aNotification: Notification) {
let contentView = ContentView(
axes: Binding (
get: {self.axes},
set: { [self] in axes = $0}))
.... // No fancy stuff
I'm open for all critique of code itself, and help: how to push this view (and all possible future subviews) to update when axes changed?

Answer 1

The thing is that #Binding is for nested Views. When you want to make changes in a SwiftUI view, you have to use the #State instead in the one where the action starts. Plus, you don't need to set an initialiser this way. You can set your value like this, inside an ObservableObject to handle your logic:
struct Axis {
var name: String
var description: String {
return "Axis: \"\(name)\""
}
}
final class AxisViewModel: ObservableObject {
#Published var axes: [Axis] = [Axis(name: "First")]
init() { handleAxes() }
func addAxis() {
axes.append(Axis(name: "New"))
handleAxes()
}
func insertAxis(at index: Int) {
axes.insert(Axis(name: "Inserted"), at: index)
handleAxes()
}
func handleAxes() {
for index in axes.indices {
var elems = Array(axes[index].name.split(separator: " "))
if elems.count > 1 {
elems.removeLast()
}
let new = elems.reduce(into:"", { $0 += "\($1) " })
axes[index].name = new + ("\(Date())")
}
}
}
struct ContentView: View {
#ObservedObject var viewModel = AxisViewModel()
var body: some View {
VStack {
ForEach(viewModel.axes.indices, id:\.self) { index in
HStack {
TextField("", text: $viewModel.axes[index].name)
Button("Insert", action: { viewModel.insertAxis(at: index) })
}
}
Button("Add", action: viewModel.addAxis)
}
}
}

Answer 2

I made a new struct Axes:
public struct Axes {
#WrappedAxes var _axes: [Axis]
public subscript (index: Int) -> Axis {
get { return _axes[index]}
set { _axes[index] = newValue}
}
// and all needed functions and vars to simulate Array behaviour:
public mutating func append(_ newElement: Axis ) {
_axes.append(newElement)
}
public mutating func insert(_ newElement: Axis, at index: Int ) {
_axes.insert(newElement, at: index)
}
public mutating func remove(at index: Int ) {
_axes.remove(at: index)
}
....
}
and put it into #ObservalbeObject:
public class Globals: ObservableObject {
#Published public var axes: Axes
....
}
Then defined AxesView as
public struct AxesView: View {
#ObservedObject var globals: Globals
public var body: some View {
...
}
...
}
That's all. For a while it works.