Undefined prop value in child component - reactjs

Question

I'm attempting to read an array item in a child component via props. Logging the array in the child component works. But if I try to access a property of one of the array items by indexing it with the :id from match.params, it tells me that I can't access a property of 'undefined'.
Any guidance would be greatly appreciated.
tours.js
import React, { Component } from "react";
import { Route, Switch } from "react-router-dom";
// Page Imports
import Summary from "../pages/summary";
import Details from "../pages/details";
// Component Imports
import Homebutton from "../components/homebutton";
class Tours extends Component {
state = {
tours: []
};
componentDidMount() {
window.scrollTo(0, 0);
fetch("/tours")
.then(res => res.json())
.then(res => this.setState({ tours: res }));
}
render() {
const tours = this.state.tours;
return (
<section className="tours-page">
<div className="center-box">
<h2>Tours</h2>
</div>
<Switch>
<Route
exact
path={this.props.match.url}
render={props => <Summary {...props} tours={tours} />}
/>
<Route
path={this.props.match.url + "/:id"}
render={props => <Details {...props} tours={tours} />}
/>
</Switch>
<Homebutton />
</section>
);
}
}
export default Tours;
details.js
import React from "react";
const Details = ({
tours,
match: {
params: { id }
}
}) => (
<section className="details">
<h2>{tours[id]["name"]}</h2>
</section>
);
export default Details;

Answer 1

To be sure that tours[id] is not undefined you should check it first
<section className="details">
<h2>{tours[id] && tours[id]["name"]}</h2>
</section>

Answer 2

As componentDidMountalways gets called after first render, you must validate your props to avoid app crashes:
const Details = ({
tours,
match: {
params: { id }
}
}) => (
<section className="details">
<h2>{tours.length && tours[id]["name"]}</h2>
</section>
);