meteor-publish-composite

Meteor.publishComposite(...) provides a flexible way to publish a set of related documents from various collections using a reactive join. This makes it easy to publish a whole tree of documents at once. The published collections are reactive and will update when additions/changes/deletions are made.

This project differs from many other parent/child relationship mappers in its flexibility. The relationship between a parent and its children can be based on almost anything. For example, let's say you have a site that displays news articles. On each article page, you would like to display a list at the end containing a couple of related articles. You could use publishComposite to publish the primary article, scan the body for keywords which are then used to search for other articles, and publish these related articles as children. Of course, the keyword extraction and searching are up to you to implement.

Installation

$ meteor add reywood:publish-composite

Usage

This package defines one new Meteor function on the server:

Meteor.publishComposite(name, options)

Arguments

• name -- string

  The name of the publication

• options -- object literal or callback function

  An object literal specifying the configuration of the composite publication or a function that returns said object literal. If a function is used, it will receive the arguments passed to Meteor.subscribe('myPub', arg1, arg2, ...) (much like the func argument of Meteor.publish). Basically, if your publication will take no arguments, pass an object literal for this argument. If your publication will take arguments, use a function that returns an object literal.

  The object literal must have a find property, and can optionally have children and collectionName properties. The find property's value must be a function that returns a cursor of your top level documents. The children property's value should be an array containing any number of object literals with this same structure. The collectionName property's value, if present, should be a string specifying an alternate collection name to publish the documents to (see this blog post for more details).

  {
      find: function() {
          // Must return a cursor containing top level documents
      },
      children: [
          {
              find: function(topLevelDocument) {
                  // Called for each top level document. Top level document is passed
                  // in as an argument.
                  // Must return a cursor of second tier documents.
              },
              children: [
                  {
                      find: function(secondTierDocument, topLevelDocument) {
                          // Called for each second tier document. These find functions
                          // will receive all parent documents starting with the nearest
                          // parent and working all the way up to the top level as
                          // arguments.
                          // Must return a cursor of third tier documents.
                      },
                      children: [
                         // Repeat as many levels deep as you like
                      ]
                  }
              ]
          },
          {
              find: function(topLevelDocument) {
                  // Also called for each top level document.
                  // Must return another cursor of second tier documents.
              }
              // The children property is optional at every level.
          }
      ]
  }

Examples

Example 1: A publication that takes no arguments.

First, we'll create our publication on the server.

// Server
Meteor.publishComposite('topTenPosts', {
    find: function() {
        // Find top ten highest scoring posts
        return Posts.find({}, { sort: { score: -1 }, limit: 10 });
    },
    children: [
        {
            find: function(post) {
                // Find post author. Even though we only want to return
                // one record here, we use "find" instead of "findOne"
                // since this function should return a cursor.
                return Meteor.users.find(
                    { _id: post.authorId },
                    { limit: 1, fields: { profile: 1 } });
            }
        },
        {
            find: function(post) {
                // Find top two comments on post
                return Comments.find(
                    { postId: post._id },
                    { sort: { score: -1 }, limit: 2 });
            },
            children: [
                {
                    find: function(comment, post) {
                        // Find user that authored comment.
                        return Meteor.users.find(
                            { _id: comment.authorId },
                            { limit: 1, fields: { profile: 1 } });
                    }
                }
            ]
        }
    ]
});

Next, we subscribe to our publication on the client.

// Client
Meteor.subscribe('topTenPosts');

Now we can use the published data in one of our templates.

<template name="topTenPosts">
    <h1>Top Ten Posts</h1>
    <ul>
        {{#each posts}}
            <li>{{title}} -- {{postAuthor.profile.name}}</li>
        {{/each}}
    </ul>
</template>

Template.topTenPosts.helpers({
    posts: function() {
        return Posts.find();
    },

    postAuthor: function() {
        // We use this helper inside the {{#each posts}} loop, so the context
        // will be a post object. Thus, we can use this.authorId.
        return Meteor.users.findOne(this.authorId);
    }
})

Example 2: A publication that does take arguments

Note a function is passed for the options argument to Meteor.publishComposite.

// Server
Meteor.publishComposite('postsByUser', function(userId, limit) {
    return {
        find: function() {
            // Find posts made by user. Note arguments for callback function
            // being used in query.
            return Posts.find({ authorId: userId }, { limit: limit });
        },
        children: [
            // This section will be similar to that of the previous example.
        ]
    }
});

// Client
var userId = 1, limit = 10;
Meteor.subscribe('postsByUser', userId, limit);

More info

For more info on how to use Meteor.publishComposite, check out these blog posts:

• Publishing Reactive Joins in Meteor
• Publishing to an Alternative Client-side Collection in Meteor