How can I check if react-router is in context?

问题

I'm migrating an AngularJS app to React little by little, and I would like to have a custom RouterLink React component that checks if react-router is in context so it can use history, and if not, falls back to usage of good old window.location. But I don't see any way of checking that in react-router's documentation.

I tried using withRouter but it throws when not in context and an ErrorBoundary doesn't seem to catch the error.

Does anyone know how I could go about doing this?

回答1:

There is Router context exposed in react-router package, i.e. __RouterContext, by using that you can check if router is avaiable:

import React, { useContext } from 'react';
import { __RouterContext } from 'react-router';

const MyComponent = (props) => {
  const router = useContext(__RouterContext);

  if (router) {
    // Router context is avaible
  } else {
    // Use window.location as router context is not availble in this component
  }

  return <SomeOtherComponent />
}

回答2:

Just wrap the hook in a try/catch:

const {useState, useEffect, Fragment} = React;
const {useLocation, MemoryRouter} = ReactRouter;

const Cmp = () => {
  let loc;
  try {
    loc = useLocation();
  } catch (err) {
    return (
      <div>No Router Available</div>
    );
  }
  return (
    <div>Hello I can see {loc.pathname}</div>
  );
};

const App1 = () => {
  return (
    <Cmp/>
  );
};

const App2 = () => {
  return (
    <MemoryRouter>
      <Cmp/>
    </MemoryRouter>
  );
};

ReactDOM.render(<App1 />, document.getElementById("app1"));
ReactDOM.render(<App2 />, document.getElementById("app2"));

<script crossorigin src="https://unpkg.com/react@16/umd/react.production.min.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.production.min.js"></script>
<script src="https://unpkg.com/react-router@5.1.2/umd/react-router.js"></script>

<div id="app1"></div>
<div id="app2"></div>

来源：https://stackoverflow.com/questions/59992359/how-can-i-check-if-react-router-is-in-context