CODEWITHSUNDEEP
node.jsmongodbapiexpressmean
anon
anon

Reputation: 2353

How to update two models in Mean App

The app has two models: users and posts. A viewing user can like (upvote) a post that is written by another user. So, I need to

  1. Add the post id to the viewing user's array of likes.
  2. Add the viewing user's id to the post's array of users that liked the post.
  3. Increment the author's counter of likes.

On a high level, I can't figure out a particularly appealing option to handle this. If I make three separate api routes, then when viewing user likes a post, three separate calls are made to the server and database.

On the other hand, if I have only one api route, it seems like it would be doing way too much. In addition, I believe I would have two nested database calls:

//Pseudocode
User.findById... // update the viewing user
   Post.findById... // update the post
      User.findById... // update the author user

I'm using express so I don't believe I can chain these one right after another (Is this what Koa allows you to do?). I can only return one response object.

How should I do this?

Upvotes: 0

Views: 192

Answers (1)

Michael Hobbs
Michael Hobbs

Reputation: 1693

I think this is more of what you are looking for. I have not tested this. I'm not entirely sure the rethrowError is needed but as a precaution I put it in until you can do some testing.

  export function update(req, res) {
    updateUserById(req.params.voterId, res, userUpvoted(req.params.postId))
      .then(updatePostById(req.params.postId, res, postLikedBy(req.params.voterId)))
      .then(updateUserById(req.params.authorId, res, userRecivedLike(req.params.voterId))
      .then(handleEntityNotFound(res))
      .then(responseWithResult(res))
      .catch(handleError(res));
  }


  // ************ Update Functions ************
  function userUpvoted(postId) {
    return function(user) {
      // update the user's upVotes
      return user;
    }
  }

  function postLikedBy(userId) {
    return function(post) {
      // update the post's upVotes
      return post;
    }
  }

  function userRecivedLike() {
    return function(entity) {
      // update the post's upVotes with the entity object
      return entity;
    }
  }
  // ************ End Update Functions ************

  // ************ UpdateBy using using callback Functions ************
  function updateUserById(id, res, updateFunction) {
    return User.findById(id)
      .then(updateFunction(res))
      .catch(rethrowError);
  }

  function updatePostById(id, res, updateFunction) {
    return Post.findById(id)
      .then(updateFunction(res))
      .catch(rethrowError);
  }
  // ************ end UpdateBy using using callback Functions ************

  // ************ Helper Functions ************
  function rethrowError(err) {
    throw err;
  }
  // ************ End Helper Functions ************

Upvotes: 1

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