Do something when Toggle state changes - ios

Question

I am using SwiftUI and want to do something when toggle state changes but I cannot find a solution for this.
How can I call a function or do whatever when toggle state changes ?
#State var condition = false
Toggle(isOn: $condition) {
Text("Toggle text here")
}

Answer 1

If you want to do something whenever the toggle state change, you may use didSet.
struct ContentView: View {
#State var condition = false{
didSet{
print("condition changed to \(condition)")
}
}
var body: some View {
let bind = Binding<Bool>(
get:{self.condition},
set:{self.condition = $0}
)
return Toggle(isOn: bind){
Text("Toggle text here")
}
}
}
When we say #State var condition = true, it's type is State<Bool> and not Bool.
when we use binding in toggle ($condition in this case), toggle directly changes the stored value. Meaning it never changes the #State, so didSet will never be triggered.
So here we create and assign to let bind an instance of Binding<Value> struct, and use that Binding struct directly in toggle. Than when we set self.condition = $0, it will trigger didSet.

Answer 2

You can use the .onChange modifier like in the first example below.
However, keep in mind that in most cases we don't need it.
In case of a view setting, you bind to a #State bool value, then you use this bool to modify the view hierarchy, as in the first example.
In case of a change in your model, you bind the toggle to a #Published value in your model or model controller. In this case, the model or model controller receive the change from the switch, do whatever is requested, and the view is rerendered. It must have an #ObservedObject reference to your model.
I show how to use the .onChange modifier in the first example. It simply logs the state.
Remember there should be as few logic as possible in SwiftUI views.
By the way that was already true far before the invention of SwiftUI ;)
Example 1 - #State value. ( Local UI settings )
import SwiftUI
struct ToggleDetailView: View {
#State var isDetailVisible: Bool = true
var body: some View {
VStack {
Toggle("Display Detail", isOn: $isDetailVisible)
.onChange(of: self.isDetailVisible, perform: { value in
print("Value has changed : \(value)")
})
if isDetailVisible {
Text("Detail is visible!")
}
}
.padding(10)
.frame(width: 300, height: 150, alignment: .top)
}
}
struct ToggleDetailView_Previews: PreviewProvider {
static var previews: some View {
ToggleDetailView()
}
}
Example 2 - #ObservedObject value. ( Action on model )
import SwiftUI
class MyModel: ObservableObject {
#Published var isSolid: Bool = false
var string: String {
isSolid ? "This is solid" : "This is fragile"
}
}
struct ToggleModelView: View {
#ObservedObject var model: MyModel
var body: some View {
VStack {
Toggle("Solid Model", isOn: $model.isSolid)
Text(model.string)
}
.padding(10)
.frame(width: 300, height: 150, alignment: .top)
}
}
struct ToggleModelView_Previews: PreviewProvider {
static var previews: some View {
ToggleModelView(model: MyModel())
}
}

Answer 3

Try
struct ContentView: View {
#State var condition = false
var body: some View {
if condition {
callMe()
}
else {
print("off")
}
return Toggle(isOn: $condition) {
Text("Toggle text here")
}
}
func callMe() {
}
}

Answer 4

Karen please check
#State var isChecked: Bool = true
#State var index: Int = 0
Toggle(isOn: self.$isChecked) {
Text("This is a Switch")
if (self.isChecked) {
Text("\(self.toggleAction(state: "Checked", index: index))")
} else {
CustomAlertView()
Text("\(self.toggleAction(state: "Unchecked", index: index))")
}
}
Add function like this
func toggleAction(state: String, index: Int) -> String {
print("The switch no. \(index) is \(state)")
return ""
}

Answer 5

I tend to use:
Toggle(isOn: $condition, label: {
Text("Power: \(condition ? "On" : "Off")")
})
.padding(.horizontal, 10.0)
.frame(width: 225, height: 50, alignment: .center)