auth-with-reach-router.jsx

let UserContext = React.createContext();

class App extends React.Component {
  state = {
    user: null,
    setUser: user => {
      this.setState({ user });
    }
  };

  render() {
    return (
      <UserContext.Provider value={this.state}>
        <Router>
          <Home path="/" />
          <About path="/about" />
          <PrivateRoute as={Dashboard} path="/dashboard" />
        </Router>
      </UserContext.Provider>
    );
  }
}

class PrivateRoute extends React.Component {
  static contextType = UserContext;

  render() {
    let { as: Comp, ...props } = this.props;
    return this.context.user ? <Comp {...props} /> : <Login />;
  }
}

class Login extends React.Component {
  static contextType = UserContext;

  render() {
    return (
      <form
        onSubmit={async () => {
          let user = await doWhateverYouNeedToDoToLogin();
          this.context.setUser(user);
        }}
      />
    );
  }
}

function Home() {
  return <div>home</div>;
}

function About() {
  return <div>about</div>;
}

function Dashboard() {
  return <div>Protected dashboard</div>;
}

@DevanB - I think this is what you were curious about.

// AuthContext

export const AuthContext = React.createContext();

export const AuthProvider = AuthContext.Provider;
export const AuthConsumer = AuthContext.Consumer;


// App.js

const App = () => {
  const [user, setUser] = useState(null);
  
  const updateUser = newUser => {
    setUser(newUser);
  }
  
  return (
    <AuthProvider
      value={{
        user,
        updateUser
      }}
    >
      <Router>
        <Home path="/" />
	<About path="/about" />
	<PrivateRoute as={Dashboard} path="/dashboard" />
      </Router>
    </AuthProvider>
  );
}


// PrivateRoute.js

const PrivateRoute = props => {
  const { user } = useContext(AuthContext);
  
  let { as: Comp, ...props } = props;
  return user ? <Comp {...props} /> : <Login />;
}


// Login.js

const Login = () => {
  const { user, updateUser } = useContext(AuthContext);
  
  return (
    <form
      onSubmit={async () => {
        let newUser = await doWhateverYouNeedToDoToLogin();
	  updateUser(newUser);
      }}
    />
  );
}


// Home.js

const Home = () => {
  return <div>home</div>;
}


// About.js

const About = () => {
  return <div>about</div>;
}


// Dashboard.js

const Dashboard = () => {
  return <div>Protected Dashboard</div>;
}

I am having issues with implementing this with nested routes. Can anyone guide me how should i go for nested private routes ? I tried nesting inside the component with router but it just doesn't render the component at all.

For nested private routes you can pass the children:

class PrivateRoute extends React.Component {
  static contextType = UserContext;

  render() {
    let { as: Comp, children, ...props } = this.props;
    return this.context.user ? <Comp {...props} >{children}</Comp> : <Login />;
  }
}

@joaodlf

+1 for Hooks, but would also love to see how this would work with purely functional components!

  const Dashboard = () => <div>dashboard</div>;
  const ProtectedRoute = ({ user }) => {
    return user != null ? (
      <Router>
        <Dashboard path="/"></Dashboard>
      </Router>
    ) : (
      <Login  />
    );
  };

  return (
     <AuthProvider
      value={{
        user,
        updateUser
      }}
    >
      <Router>
        <ProtectedRoute path="/" user={user} />
      </Router>
    </AuthProvider>
  );
}

this is how I implemented PrivateRoute

const PrivateRoute = props => {
  const { user } = useUserContext();
  let { as: Comp, ...otherProps } = props;

  return user ? (
    <Comp {...otherProps} />
  ) : (
    <Redirect to="/login" replace={true} noThrow={true} />
  );
};

Make sure noThrow props is set to true otherwise you'll get exception when redirecting in development.

@christensen143 I like your hooks example but think

// PrivateRoute.js

const PrivateRoute = props => {
  const { user } = useContext(AuthContext);
  
  let { as: Comp, ...props } = props;
  return user ? <Comp {...props} /> : <Login />;
}

Should be

// PrivateRoute.js

const PrivateRoute = props => {
  const { user } = useContext(AuthContext);
  
  let { as: Comp, ...restOfTheProps } = props;
  return user ? <Comp {...restOfTheProps } /> : <Login />;
}

to avoid an Identifier 'props' has already been declared error.

Make sure noThrow props is set to true otherwise you'll get exception when redirecting in development.

@cvrajeesh you fixed my problem. thank you!

For the people that show up here for how to do this with nested routing, I solved it using nested routers:

// App.js

<Router>
   <Login path="/login" />
   <ForgotPass path="/forgot-password" />
   <PrivateRoute as={Dashboard} path="/dashboard/*" />
</Router>

// Dashboard
export default ({children}) => (
  <Router>
    <DashHome path="/" />
    <DashStatistics path="/statistics" />
  </Router>
)

New to this. My <Router> moans that I don't have path as a prop in the children components I pass. What happens when you have dynamically created pages (like blog posts) in your gatsby-node.js? Can't I just have...

<Router>
  {authenticated && <PrivateRoute/>}
  {!authenticated && <PublicRoute/>}
</Router>

...and then not have to think about it further down the component tree? Rather than pepper my whole application with <Component path="path/to/something"/>?

Also, does <Router/> effectively stop Gatsby from serving static files?