Optional extension with custom binding in SwiftUI - swift

Question

Is there a way to create an extension for Optional value so that we don't need to create custom binding individually.
class ViewModel: ObservableObject {
#Published var text: String?
}
struct ContentView: View {
#ObservedObject var model: ViewModel
var body: some View {
let binding = Binding(
get: { self.model.text ?? "" },
set: { self.model.text = $0 }
)
return VStack {
TextField("Text", text: binding)
}
}
}
I'm thinking about doing something like this
extension Optional where Wrapped == String {
func optionalBinding() -> Binding<String> {
return Binding(get: {
self ?? ""
}, set: { newValue in
self = newValue
})
}
}
Any suggestions on this?

Answer 1

You may try extending Binding instead of Optional:
extension Binding where Value == String? {
var optionalBinding: Binding<String> {
.init(
get: {
self.wrappedValue ?? ""
}, set: {
self.wrappedValue = $0
}
)
}
}
And use it like this:
class ViewModel: ObservableObject {
#Published var text: String?
}
struct ContentView: View {
#ObservedObject var model = ViewModel()
var body: some View {
VStack {
TextField("Text", text: $model.text.optionalBinding)
Text(String(describing: model.text))
}
}
}

Answer 2

Nil-coalescing operator.
public extension Binding {
static func ?? <Wrapped>(optional: Self, defaultValue: Wrapped) -> Binding<Wrapped>
where Value == Wrapped? {
.init(
get: { optional.wrappedValue ?? defaultValue },
set: { optional.wrappedValue = $0 }
)
}
}
var wrappedValue: String? = "📬"
#Binding(
get: { wrappedValue },
set: { wrappedValue = $0 }
) var string;
let stringOrDefault = $string ?? "📭"
XCTAssertEqual(stringOrDefault.wrappedValue, "📬")
string = nil
XCTAssertEqual(stringOrDefault.wrappedValue, "📭")
stringOrDefault.wrappedValue = "📪"
XCTAssertEqual(string, "📪")

Answer 3

To build on #pawello2222's answer, you can use a more generic extension catching all values:
extension Binding {
func unwrapped<T>(_ defaultValue: T) -> Binding<T> where Value == Optional<T> {
let binding = Binding<T>(get: { self.wrappedValue ?? defaultValue }, set: { self.wrappedValue = $0 })
return binding
}
}
And it is used like:
class ViewModel: ObservableObject {
#Published var text: String?
}
struct ContentView: View {
#ObservedObject var model = ViewModel()
var body: some View {
VStack {
TextField("Text", text: $model.text.unwrapped(String()))
Text(String(describing: model.text))
}
}
}