SwiftUI/Examples/React Meets SwiftUI/Context.md

Context

You can replicate the context functionality found in React by using a combination of BindableObject, Combine and defining an environmentObject for a View. You create a class that adheres to the BindableObject and provide that as an argument to environmentObject when initiating your parent view. Any child of that parent view can then access the class using @EnvironmentObject.

React

import React, { useContext } from "react";

const Session = React.createContext({ name: "" });

export function ContextProvider() {
  return (
    <Session.Provider value={{ name: "Bento" }}>
      <Parent />
    </Session.Provider>
  );
}

export function Parent() {
  return <Child />;
}

export function Child() {
  const session = useContext(Session);

  return <span>Hello {session.name}</span>;
}

SwiftUI

import SwiftUI
import Combine

final class Session: BindableObject {
    let didChange = PassthroughSubject<Session, Never>()

    var name: String {
        didSet { didChange.send(self) }
    }

    init(name: String) {
        self.name = name
    }
}


struct ContextProvider : View {
    var body: some View {
        Parent().environmentObject(Session(name: "Bento"))
    }
}

struct Parent : View {
    var body: some View {
        Child()
    }
}

struct Child : View {

    @EnvironmentObject var session: Session

    var body: some View {
        Text("Hello \(session.name)")
    }
}