componentWillReceiveProps state is different from render state after redux state update

Question

First of all, all the relevant code (click on the filename for the full source code of that file).

LoginView.js

LoginView = class extends React.Component {
    handleLogin = (email, password) => {
        this.props.authenticationActionCreator.login(email, password);
    };

    componentWillMount () {
        console.log('componentWillMount', 'this.props.isAuthenticated', this.props.isAuthenticated);
    }

    componentWillReceiveProps () {
        console.log('componentWillReceiveProps', 'this.props.isAuthenticated', this.props.isAuthenticated);
    }

    render () {
        let {
            errorMessage,
            isAuthenticating
        } = this.props;

        return <div>
            <p>this.props.isAuthenticated: {this.props.isAuthenticated ? 'true' : 'false'}</p>
            <button onClick={() => {
                this.handleLogin('[email protected]', 'nosyte');
            }}>Login</button>
        </div>;
    }
};

authentication.js (reducer)

if (action.type === 'AUTHENTICATION.LOGIN_SUCCESS') {
    return initialState.merge({
        isAuthenticated: true,
        token: action.data.token,
        user: action.data.user
    });
}

authenticationActionCreator.js

authenticationActionCreator.loginSuccess = (token) => {
    let decodedToken;

    // @todo Handle failure to decode token.

    decodedToken = jwtDecode(token);

    localStorage.setItem('token', token);

    return {
        type: 'AUTHENTICATION.LOGIN_SUCCESS',
        data: {
            token,
            user: decodedToken.user
        }
    };
};

The flow is simple:

1. User opens the page.
2. User clicks the <button /> that invokes authenticationActionCreator.login.

The console.log output is:

componentWillMount this.props.isAuthenticated true
action AUTHENTICATION.LOGIN_REQUEST @ 16:52:50.880
componentWillReceiveProps this.props.isAuthenticated true
componentWillReceiveProps this.props.isAuthenticated false
action AUTHENTICATION.LOGIN_SUCCESS @ 16:52:51.975

The expected console.log output is:

componentWillMount this.props.isAuthenticated true
action AUTHENTICATION.LOGIN_REQUEST @ 16:52:50.880
componentWillReceiveProps this.props.isAuthenticated false
action AUTHENTICATION.LOGIN_SUCCESS @ 16:52:51.975
componentWillReceiveProps this.props.isAuthenticated true

The problem is that render has the correct state (the state after AUTHENTICATION.LOGIN_SUCCESS) and componentWillReceiveProps has the old state (the state after AUTHENTICATION.LOGIN_REQUEST).

I am the last call to componentWillReceiveProps to have the same state object as the render method.

Is this:

• a bug
• I am doing something wrong
• my expectations are false

?

Answer 1

It took me writing all this debug trace/question to remember that componentWillReceiveProps API is:

componentWillReceiveProps: function(nextProps) {}

In other words, my LoginView.js example should have been:

LoginView = class extends React.Component {
    handleLogin = (email, password) => {
        this.props.authenticationActionCreator.login(email, password);
    };

    componentWillReceiveProps (nextProps) {
        console.log('componentWillReceiveProps', 'nextProps.isAuthenticated', nextProps.isAuthenticated);
    }

    render () {
        let {
            errorMessage,
            isAuthenticating
        } = this.props;

        return <div>
            <p>this.props.isAuthenticated: {this.props.isAuthenticated ? 'true' : 'false'}</p>
            <button onClick={() => {
                this.handleLogin('[email protected]', 'nosyte');
            }}>Login</button>
        </div>;
    }
};