iOS 16 Compatible onChange with Old Values

The Problem

iOS 17’s onChange(of:old:new:) provides both previous and current values. iOS 16 only has onChange(of:) with the new value.

Solution: Closure Capture

import SwiftUI

public extension View {
    @ViewBuilder
    func onChangeCompat<V>(
        for value: V,
        _ action: @escaping (_ previous: V, _ current: V) -> Void
    ) -> some View where V: Equatable {
        if #available(iOS 17, *) {
            onChange(of: value, action)
        } else {
            onChange(of: value) { [value] newValue in
                action(value, newValue)
            }
        }
    }
}

The [value] capture list preserves the old value at the moment onChange is attached.

Practical Extension: onTransition

public extension View {
    func onTransition<V: Equatable>(
        of value: V,
        from reference: V,
        perform action: @escaping () -> Void
    ) -> some View {
        onChangeCompat(for: value) { oldValue, newValue in
            if oldValue == reference && newValue != reference {
                action()
            }
        }
    }
}

Triggers action when value moves away from a specific state:

@State private var loadingState: LoadingState = .loading

Text("Data")
    .onTransition(of: loadingState, from: .loading) {
        hapticFeedback.success()
    }

What do you think about this solution? Let me know in the comments!