SwiftUI: how to make an enum allCases observable? - swiftui

Question

I come from the UIKit universe and am struggling to understand SwiftUI's object observers.
Here is what I have:
MyEnum
enum MyEnum: String, Identifiable, CaseIterable {
static var all: [MyEnum] { MyEnum.allCases.sorted(by: { $0.value > $1.value }) }
case value1 = "value1"
case value2 = "value2"
var value: Double { UserDefaults.standard.double(forKey: rawValue) }
}
I also have a service that calls an API and updates all the MyEnum values (by setting the new value in the UserDefaults).
And the UI:
struct ContentView: View {
var body: some View {
TestHeader()
TestList()
}
}
struct TestHeader: View {
var body: some View {
Button {
APIService.reloadAll()
}, label: {
Text("Update")
}
}
}
struct TestList: View {
var body: some View {
List {
ForEach(MyEnum.all) {
MyEnumRow(myEnum: $0)
.listRowInsets(EdgeInsets())
}
}
.listStyle(PlainListStyle())
}
}
struct MyEnumRow: View {
var myEnum: MyEnum
var body: some View {
HStack(spacing: 10) {
Text(myEnum.rawValue)
Text(myEnum.value)
}
}
}
Of course when I tap the update button the myEnum list isn't updated, but I don't know how to make it responsive to content change. Could you please help me?

Answer 1

You can use #AppStorage to watch a particular value in UserDefaults. This is slightly more complex in your case because you don't know what key to be watching until the view is created. I opted to have the AppStorage passed in from the parent view.
struct ContentView: View {
var body: some View {
TestHeader()
TestList()
}
}
struct TestHeader: View {
var body: some View {
Button(action: {
UserDefaults.standard.set(Double(Date().timeIntervalSince1970), forKey: MyEnum.allCases.first!.rawValue)
}) {
Text("Update")
}
}
}
struct TestList: View {
var body: some View {
List {
ForEach(MyEnum.all) {
MyEnumRow(myEnum: $0, valueStorage: AppStorage(wrappedValue: 0, $0.rawValue))
.listRowInsets(EdgeInsets())
}
}
.listStyle(PlainListStyle())
}
}
struct MyEnumRow: View {
var myEnum: MyEnum
#AppStorage var valueStorage : Double
var body: some View {
HStack(spacing: 10) {
Text(myEnum.rawValue)
Text("\(valueStorage)")
}
}
}
enum MyEnum: String, Identifiable, CaseIterable {
static var all: [MyEnum] { MyEnum.allCases.sorted(by: { $0.value > $1.value }) }
case value1 = "value1"
case value2 = "value2"
var value: Double { UserDefaults.standard.double(forKey: rawValue) }
var id: String { self.rawValue }
}