Cascading Action system for SwiftUI. Read more about it here: http://www.magnuskahr.dk/posts/2021/12/cascading-environment-actions-in-swiftui/

CascadingAction.swift

import SwiftUI

extension View {
    func cascadingAction<ActionInput>(path: CascadingActionNodeModifier<ActionInput>.Path, handler: @escaping (ActionInput) -> Void) -> some View {
        self.modifier(CascadingActionNodeModifier(path: path, handler: handler))
    }
    
    func cascadingAction(path: CascadingActionNodeModifier<Void>.Path, handler: @escaping () -> Void) -> some View {
        self.modifier(CascadingActionNodeModifier(path: path, handler: handler))
    }
}

struct CascadingActionNodeModifier<ActionInput>: ViewModifier {
    
    typealias Path = WritableKeyPath<EnvironmentValues, CascadingAction<ActionInput>>
    
    @Environment private var parent: CascadingAction<ActionInput>
    let handler: (ActionInput) -> Void
    let path: Path
    
    init(path: Path, handler: @escaping (ActionInput) -> Void) {
        self._parent = Environment(path)
        self.handler = handler
        self.path = path
    }
    
    func body(content: Content) -> some View {
        content.environment(path, node)
    }
    
    private var node: CascadingAction<ActionInput> {
        .node(parent: parent, action: handler)
    }
}

indirect enum CascadingAction<Input> {
    
    typealias Action = (Input) -> Void
    
    case root
    case node(parent: Self, action: Action)
    
    func callAsFunction(_ input: Input) {
        if case let .node(parent, action) = self {
            action(input)
            parent(input)
        }
    }
}

extension CascadingAction where Input == Void {
    func callAsFunction() {
        self.callAsFunction(_: ())
    }
}