Updating Redux state does not trigger componentWillReceiveProps

Question

I\'m trying to validate the login information. After making sure the login is valid I want to fire a new route. I pass the state.loginReducer.login as props. When I handle t

Answer 1

If state.loginReducer.login changes, then componentWillReceiveProps will get triggered. If you believe your reducer is returning a new state, and componentWillReceiveProps is not being triggered, make sure that the new state is immutable. Returning the same state reference thats passed to the reducer won't work.

From https://github.com/reactjs/redux/blob/master/docs/Troubleshooting.md

This is wrong:

function todos(state = [], action) {
  switch (action.type) {
  case 'ADD_TODO':
    // Wrong! This mutates state
    state.push({
      text: action.text,
      completed: false
    });
  case 'COMPLETE_TODO':
    // Wrong! This mutates state[action.index].
    state[action.index].completed = true;
  }

  return state;
}

This is right:

function todos(state = [], action) {
  switch (action.type) {
  case 'ADD_TODO':
    // Return a new array
    return [...state, {
      text: action.text,
      completed: false
    }];
  case 'COMPLETE_TODO':
    // Return a new array
    return [
      ...state.slice(0, action.index),
      // Copy the object before mutating
      Object.assign({}, state[action.index], {
        completed: true
      }),
      ...state.slice(action.index + 1)
    ];
  default:
    return state;
  }
}