组件不会在setState上呈现，始终重定向

Question

我正在尝试基于身份验证呈现组件。如果用户未经过身份验证，则会将其重定向到登录页面。

无论我做什么，如果我直接转到/路由，登录组件将继续呈现。

即使isAuthenticated为真且视图重新渲染，我也无法渲染仪表板。我究竟做错了什么？是否有承诺？

class App extends React.Component {
    constructor(props){
        super()
        this.state = {
            isAuthenticated: false
        }
    }
    componentWillMount(){
        this.authenticate()
    }
    authenticate(){
        fetch("http://localhost:3000/authenticated", {
            method: "POST",
            headers: {
                "Accept": "application/json",
                "Content-type": "application/json"
            },
            body: JSON.stringify({
                token: localStorage.getItem("token")
            })
        })
        .then(res => res.json())
        .then(data => {
            if(data.success){
                this.setState({             // Re-render
                    isAuthenticated: true
                })
            }
        })
        .catch(err => {
            console.log(err);
        });
    }

    render() {
        return(
            <Router>
                <div id="container">
                    // First time false. After setState it's true.
                    {console.log("render", this.state.isAuthenticated)}

                    <Route exact path="/" render={() => {
                        // First time false. After setState, doesn't log.
                        console.log("auth", this.state.isAuthenticated);

                        return this.state.isAuthenticated
                        ? <Dashboard />
                        : <Redirect to="/login"/>
                    }}/>

                </div>
            </Router>
        )
    }
}