using …spread, but redux still throws warning about state mutation

Question

Redux throws Warning on dispatch:

Error: A state mutation was detected inside a dispatch, in the path: 
roundHistory.2.tickets. Take a look at the reducer(s)         


        

Answer 1

Okay i got it. Spreading an array of objects gives a new array but with links to same objects. To avoid the mutation, i added this line: archive[i] = {...state.roundHistory[i]};

case 'ARCHIVE_TICKETS' :
  var archive = [...state.roundHistory];
  for (var i in archive) {
    archive[i] = {...state.roundHistory[i]};
    if (archive[i]._id === action.roundId) {
      archive[i].tickets = action.data;
    }
  }
  return Object.assign({}, state, {
    roundHistory: archive
  });