SwiftUI Picker onChange or equivalent?

Question

I want to change some other unrelated @State variable when a Picker gets changed but there is no onChanged and it\'s not possible to p

Answer 1

I use a segmented picker and had a similar requirement. After trying a few things I just used an object that had both an ObservableObjectPublisher and a PassthroughSubject publisher as the selection. That let me satisfy SwiftUI and with an onReceive() I could do other stuff as well.

// Selector for the base and radix
Picker("Radix", selection: $base.value) {
    Text("Dec").tag(10)
    Text("Hex").tag(16)
    Text("Oct").tag(8)
}
.pickerStyle(SegmentedPickerStyle())
// receiver for changes in base
.onReceive(base.publisher, perform: { self.setRadices(base: $0) })

base has both an objectWillChange and a PassthroughSubject<Int, Never> publisher imaginatively called publisher.

class Observable<T>: ObservableObject, Identifiable {
    let id = UUID()
    let objectWillChange = ObservableObjectPublisher()
    let publisher = PassthroughSubject<T, Never>()
    var value: T {
        willSet { objectWillChange.send() }
        didSet { publisher.send(value) }
    }

    init(_ initValue: T) { self.value = initValue }
}

typealias ObservableInt = Observable<Int>

Defining objectWillChange isn't strictly necessary but when I wrote that I liked to remind myself that it was there.