React Native redux reducers best way to push array

Question

I have the following state and reducer but it's not pushing in the new array object.

const initialState = {
    photos: [],
    selectedPhoto:{},
    photosTeamId:'',
    photosProjectId:''
};

case actionTypes.PHOTOS_UPDATE:
            return Object.assign({}, state, {
                photos:action.data.photos,
                photosTeamId:action.data.photosTeamId,
                photosProjectId:action.data.photosProjectId
            })

photos is not getting pushed but overwritten

See this https://stackoverflow.com/questions/43376849/use-object-assign-or-spread-operator-in-react-redux-which-is-a-better-practise/43376980#43376980 and this https://stackoverflow.com/questions/41949387/how-to-use-immutability-helper-to-update-a-nested-object-within-an-array/41949486#41949486. You can either go with Spread operator syntax or Immutability-helper package — Shubham Khatri, Nov 02 '17 at 08:12

score 2 · Accepted Answer · answered Nov 02 '17 at 06:53

Here's a more cleaner way using javascript spread syntax:

const initialState = {
    photos: [],
    selectedPhoto:{},
    photosTeamId:'',
    photosProjectId:''
};

case actionTypes.PHOTOS_UPDATE:
            return {
                ...state,
                photos: [...state.photos, ...actions.data.photos],
                photosTeamId: action.data.photosTeamId,
                photosProjectId: action.data.photosProjectId
            }

score 0 · Answer 2 · answered Nov 02 '17 at 06:35

0

case actionTypes.PHOTOS_UPDATE:
  return {
    ...state,
    photos: state.photos.concat(action.data.photos),
    photosTeamId: action.data.photosTeamId,
    photosProjectId: action.data.photosProjectId
  };

answered Nov 02 '17 at 06:35

vinayr

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score 0 · Answer 3 · answered Nov 02 '17 at 06:43

Here's the spread operator […]. The spread operator can be used to take an existing array and add another element to it while still preserving the original array.

Example:

case actionTypes.PHOTOS_UPDATE:
  return [
    ...state,
    Object.assign({}, {
      photos:action.data.photos,
      photosTeamId:action.data.photosTeamId,
      photosProjectId:action.data.photosProjectId
    })
  ];

React Native redux reducers best way to push array

3 Answers3

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