27. Updating Data on the Server

Video Link

We'll start by changing the toggleTodo action creator to be a thunk action creator, so we add dispatch as a curried argument. Next, we'll call the toggleTodo API endpoint, and wait for the response to come back.

When the response is available, we will dispatch an action with the type 'TOGGLE_TODO_SUCCESS', and the response. We'll usenormalizeagain by passing the originalresponse` as the first argument, and the todo schema as the second argument.

Updated toggleTodo Action Creator
export const toggleTodo = (id) => (dispatch) =>
  api.toggleTodo(id).then(response => {
      type: 'TOGGLE_TODO_SUCCESS',
      response: normalize(response, schema.todo),

Updating the ids Reducer

Inside of createList.js we will add a new case for the 'TOGGLE_TODO_SUCCESS' action.

We'll extract the code for this case into a separate function called handleToggle, and pass in the state and the action.

// Inside the `ids` reducer
    return handleToggle(state, action);

We'll put our handleToggle function above the ids reducer. It accepts the state (an array of ids) and the 'TOGGLE_TODO_SUCCESS' action.

We will destructure the result as the toggledId and the entities from the normalized response. Next, we will read the completed value from the todo, which I get by referencing entities.todos by the toggledId.

There are two cases in which we want to remove the todo from the list:

  • The completed field is true but the filter is active
  • completed is false but the filter is completed

When shouldRemove is true, we want to return a copy of the list that does not contain the id of the todo that was just toggled. We accomplish this by filtering the list by id and only leave the ones that have a different id. Otherwise, we return the original array.

Completed handleToggle Function
const handleToggle = (state, action) => {
  const { result: toggledId, entities } = action.response;
  const { completed } = entities.todos[toggledId];
  const shouldRemove = (
    (completed && filter === 'active') ||
    (!completed && filter === 'completed')
  return shouldRemove ?
    state.filter(id => id !== toggledId) :

Demonstration and recap at 3:20 in video

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