Meteor/React - Update subscription on state change

Question

I'm in trouble with subscription and React, maybe i don't do it the right way.

Here is the problem : i'd like to create a page with a movies list provided by a mongo collection, there is also a genre filter and a "load more" button.

When i use load more only, i update publication to skip existing item and return new ones, it work well.

When i change my genre filter, i simply update my publication with that filter, work fine too...

But if i do that two actions together, for example : load more, then filter by genre, the results looks bad and seems to keep old results, pagination isn't reseted to default value.

Here is a simplified version of my code.

Server side publication :

Meteor.publish('movies.published', function ( sort = null, skip = 0, limit = 20, filters = {} ) {

  if ( ! sort || typeof sort !== 'object' ) {
    sort = {releaseDate: -1};
  }

  let params = Object.assign({
    webTorrents: {
      $exists: true,
      $ne: []
    },
    status: 1,
  }, filters);

  console.log( '----------------Publishing--------------------');

  let cursor = Movies.find(params, {
    sort: sort,
    skip: skip,
    limit: limit
  });

  // Test publication
  // Count is always good
  console.log(cursor.fetch().length);

  return cursor;

});

Client side component :

import React from "react";
import TrackerReact from "meteor/ultimatejs:tracker-react";

import Movies from "/imports/api/movies/movies.js";
import Genres from "/imports/api/genres/genres.js";

const itemPerPage = 1; // let's say 1 item to simplify our test 
const defaultOrder = 'releaseDate';

export default class Home extends TrackerReact(React.Component) {

  constructor(props) {
    super(props);

    let options = Object.assign(Meteor.settings.public.list.options, {genres: Genres.find()});

    this.state = {
      subscription: {
        movies: Meteor.subscribe('movies.published', {[defaultOrder]: -1}, 0, itemPerPage),
      },
      filters: {},
      sort: defaultOrder,
      options: options,
    };
  }

  componentWillUnmount() {
    this.state.subscription.movies.stop();
  }

  filterByGenre(event) {
    let filterGenre = {
      ['genres.slug']: event.target.value !== '' ? event.target.value : {$ne: null}
    };
    this.updateFilters(filterGenre);
  }

  updateFilters( values ) {

    // Merge filters
    let filters = Object.assign(this.state.filters, values);
    console.log('updating filters', filters);

    // Update subscription with filters values
    // here i must reset the pagination
    this.state.subscription.movies.stop();
    let newSubscription = Object.assign({}, this.state.subscription, {
      movies: Meteor.subscribe('movies.published', {[this.state.sort]: -1}, 0, itemPerPage, filters),
    });

    this.setState({
      subscription: newSubscription,
      filters: filters,
    })

  }

  loadMore( skip ) {

    // Add an item
    let newSubscription = Object.assign({}, this.state.subscription, {
      movies: Meteor.subscribe('movies.published', {[this.state.sort]: -1}, skip, itemPerPage, this.state.filters),
    });

    this.setState({
      subscription: newSubscription,
    });

  }

  render() {

    if ( ! this.state.subscription.movies.ready() ) {
      return ( <div>loading...</div> );
    }

    // Get our items
    let movies = Movies.find().fetch();

    return (
            <div>

                <div className="container-fluid">

          {/* Filters */}
          <form className="form form-inline">
            <div className="form-group m-r m-2x">
              <select className="form-control" value={this.state.filters['genres.slug'] && this.state.filters['genres.slug']} onChange={this.filterByGenre.bind(this)}>
                <option value="">Genres</option>
                {this.state.options.genres.map((genre, key) => {
                  return <option key={key} value={genre.slug}>{genre.name}</option>
                })}
              </select>
            </div>
          </form>

          <hr />

          {/* list */}
          <div className="row list">
            {movies.map((movie) => {
              return (
                <div key={movie._id} className="col-xs-2">{movie.title}</div>
              )
            })}
          </div>

          {/* Load more */}
          <button id="load-more" type="button" className="btn btn-sm btn-info" onClick={this.loadMore.bind(this, movies.length)}>
            Load more
          </button>

                </div>

        <div className="col-xs-3 pull-right text-right">{movies.length} movies</div>

        <hr />

            </div>
    )

  }

}

Here is a better way to do that ? Thanks for your help !

Answer 1

I founded what was the problem. When using the method loadMore, i don't stop the old subscription (i want to keep old items and add the new ones), the problem is that "addMore" subscription was keeped in my subscriptions array (see Meteor.default_connection._subscriptions). So when i change filters i close only the last "loadMore" subscription...

2 solutions :

• Loop through Meteor.default_connection._subscriptions, to close old "LoadMore" subscriptions.
• Keep a copy of old items in a array and merge them with new ones after subscription was updated, that what i did.

Updated client code :

import React from "react";
import TrackerReact from "meteor/ultimatejs:tracker-react";

import Movies from "/imports/api/movies/movies.js";
import Genres from "/imports/api/genres/genres.js";

const itemPerPage = 1;
const defaultOrder = 'releaseDate';

export default class Home extends TrackerReact(React.Component) {

  constructor(props) {
    super(props);

    let options = Object.assign(Meteor.settings.public.list.options, {genres: Genres.find()});

    this.state = {
      subscription: {
        movies: Meteor.subscribe('movies.published', {[defaultOrder]: -1}, 0, itemPerPage),
        moviesCount: Meteor.subscribe('movies.count'),
      },
      skip: 0,
      filters: {},
      sort: defaultOrder,
      options: options,
    };

    // our local data
    this.data = [];
    this.previous = [];
  }

  componentWillUnmount() {
    this.state.subscription.movies.stop();
  }

  filterByGenre(event) {
    let filterGenre = {
      ['genres.slug']: event.target.value !== '' ? event.target.value : {$ne: null}
    };
    this.updateFilters(filterGenre);
  }

  updateFilters( values ) {

    // Merge filters
    let filters = Object.assign(this.state.filters, values);

    // Update subscription ( reset pagination )
    this.state.subscription.movies.stop();
    this.state.subscription.moviesCount.stop();
    let newSubscription = Object.assign({}, this.state.subscription, {
      movies: Meteor.subscribe('movies.published', {[this.state.sort]: -1}, 0, itemPerPage, filters),
      moviesCount: Meteor.subscribe('movies.count', filters),
    });

    this.setState({
      subscription: newSubscription,
      filters: filters,
      skip: 0,
    });

  }

  loadMore() {

    // Keep a copy of previous page items
    this.previous = this.data;

    // Update subscription
    this.state.subscription.movies.stop();
    let newSubscription = Object.assign({}, this.state.subscription, {
      movies: Meteor.subscribe('movies.published', {[this.state.sort]: -1}, this.previous.length, itemPerPage, this.state.filters)
    });

    this.setState({
      subscription: newSubscription,
      skip: this.previous.length,
    });

  }

  getMovies() {

    // Wait subscription ready to avoid replacing items
    if ( ! this.state.subscription.movies.ready() ) {
      return this.previous;
    }

    // Get new data and merge with old ones
    let newData = Movies.find().fetch();
    this.data = this.previous.concat(newData);

    // Reset previous array
    this.previous = [];

    return this.data;
  }

  render() {

    if ( ! this.state.subscription.movies.ready() && ! this.previous.length ) {
      return ( <div>loading...</div> );
    }

    // Get our items
    let movies = this.getMovies();

    return (
      <div>

        <div className="container-fluid">

          {/* Filters */}
          <form className="form form-inline">
            <div className="form-group m-r m-2x">
              <select className="form-control" value={this.state.filters['genres.slug'] && this.state.filters['genres.slug']} onChange={this.filterByGenre.bind(this)}>
                <option value="">Genres</option>
                {this.state.options.genres.map((genre, key) => {
                  return <option key={key} value={genre.slug}>{genre.name}</option>
                })}
              </select>
            </div>
          </form>

          <hr />

          {/* list */}
          <div className="row list">
            {movies.map((movie) => {
              return (
                <div key={movie._id} className="col-xs-2">{movie.title}</div>
              )
            })}
          </div>

          {/* Load more */}
          <div className="row">
            <div className="col-xs-12 text-center">
              {Counts.get('movies.count') > movies.length &&
                <button id="load-more" type="button" className="btn btn-sm btn-info" onClick={this.loadMore.bind(this)}>
                  Load more
                </button>
              }
            </div>
          </div>

        </div>

        <div className="col-xs-3 pull-right text-right">{Counts.get('movies.count')} movies</div>

        <hr />

      </div>
    )

  }

}

I hope it will help !