How to implement custom callback action in SwiftUI? Similar to onAppear functionality - swift

Question

I have custom ActionView with two buttons: Car and Bike. When these buttons tapped I need that in the MainView modifiers onCarTap/onBikeTap will be triggered.
With my current implementation here is error:
Argument passed to call that takes no arguments
Value of tuple type 'Void' has no member 'onBikeTap'
Source code:
struct ActionView: View {
// Callback for button taps
var onCarTap: (() -> Void)?
var onBikeTap: (() -> Void)?
var body: some View {
HStack {
Button(action: {
onCarTap?()
}, label: {
Text("Car")
})
Button(action: {
onBikeTap?()
}, label: {
Text("Bike")
})
}
}
}
I am looking for solution like this:
struct MainView: View {
var body: some View {
ActionView()
.onCarTap({})
.onBikeTap({ })
}
}
It is possible to implement in this way:
ActionView(onCarTap: {
print("on car tap")
}, onBikeTap: {
print("on bike tap")
})

Answer 1

Assuming you have the following View:
struct ActionView: View {
var onCarTapAction: (() -> Void)?
var onBikeTapAction: (() -> Void)?
var body: some View {
HStack {
Button(action: {
onCarTapAction?()
}, label: {
Text("Car")
})
Button(action: {
onBikeTapAction?()
}, label: {
Text("Bike")
})
}
}
}
You can create an extension:
extension ActionView {
func onCarTap(action: #escaping (() -> Void)) -> ActionView {
ActionView(onCarTapAction: action, onBikeTapAction: onBikeTapAction)
}
func onBikeTap(action: #escaping (() -> Void)) -> ActionView {
ActionView(onCarTapAction: onCarTapAction, onBikeTapAction: action)
}
}
and use it like this:
struct ContentView: View {
var body: some View {
ActionView()
.onCarTap {
print("onCarTap")
}
.onBikeTap {
print("onBikeTap")
}
}
}

Answer 2

You can declare a modifier for your purpose like the following.
extension ActionView {
func onCarTap(_ handler: #escaping () -> Void) -> ActionView {
var new = self
new.onCarTap = handler
return new
}
}
In addition, if you prefer to hide the handler property with private or fileprivate to prevent to be accessed directly, have to declare a designated init which accepts parameters for its properties except one for the handler.