04-collections.md.erb

---
title: Collections
slug: collections
date: 0004/01/01
number: 4
contents: Learn about Meteor's core feature, realtime collections.|Understand how Meteor's data synchronization works.|Integrate collections with our templates.|Turn our basic prototype into a functioning realtime application!
paragraphs: 72
---

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~~~js
Posts = new Meteor.Collection('posts');
~~~
<%= caption "collections/posts.js" %>

<%= commit "4-1", "Added a posts collection" %>

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<% note do %>

### To Var Or Not To Var?

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<% end %>

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<% note do %>

### Console vs Console vs Console

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#### Terminal

<%= screenshot "terminal", "The Terminal" %>

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#### Browser Console

<%= screenshot "browser-console", "The Browser Console" %>

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#### Mongo Shell

<%= screenshot "mongo-shell", "The Mongo Shell" %>

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<% end %>

### Server-Side Collections

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~~~bash
> db.posts.insert({title: "A new post"});

> db.posts.find();
{ "_id": ObjectId(".."), "title" : "A new post"};
~~~
<%= caption "The Mongo Shell" %>

<% note do %>

### Mongo on Meteor.com

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<% end %>

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### Client-Side Collections

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<% note do %>

### Introducing MiniMongo

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<% end %>

### Client-Server Communication

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~~~bash
> db.posts.find();
{title: "A new post", _id: ObjectId("..")};
~~~
<%= caption "The Mongo Shell" %>

~~~js
❯ Posts.findOne();
{title: "A new post", _id: LocalCollection._ObjectID};
~~~
<%= caption "First browser console" %>

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~~~js
❯ Posts.find().count();
1
❯ Posts.insert({title: "A second post"});
'xxx'
❯ Posts.find().count();
2
~~~
<%= caption "First browser console" %>

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~~~bash
❯ db.posts.find();
{title: "A new post", _id: ObjectId("..")};
{title: "A second post", _id: 'yyy'};
~~~
<%= caption "The Mongo Shell" %>

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~~~js
❯ Posts.find().count();
2
~~~
<%= caption "Second browser console" %>

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### Keeping it Real-time

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### Populating the Database

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~~~bash
$ meteor reset
~~~

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~~~js
if (Posts.find().count() === 0) {
  Posts.insert({
    title: 'Introducing Telescope',
    author: 'Sacha Greif',
    url: 'https://sachagreif.com/introducing-telescope/'
  });
  
  Posts.insert({
    title: 'Meteor',
    author: 'Tom Coleman',
    url: 'https://meteor.com'
  });
  
  Posts.insert({
    title: 'The Meteor Book',
    author: 'Tom Coleman',
    url: 'https://themeteorbook.com'
  });
}
~~~
<%= caption "server/fixtures.js" %>

<%= commit "4-2", "Added data to the posts collection." %>

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### Wiring the data to our HTML with helpers

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~~~js
❯ Posts.find().fetch();
~~~
<%= caption "Browser console" %>

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~~~js
Template.postsList.helpers({
  posts: function() {
    return Posts.find();
  }
});
~~~
<%= caption "client/views/posts/posts_list.js" %>
<%= highlight "2~4" %>

<%= commit "4-3", "Wired collection into `postsList` template." %>

<% note do %>

### Find & Fetch

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<% end %>

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<%= screenshot "4-3", "Using live data" %>

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~~~js
❯ Posts.insert({
  title: 'Meteor Docs', 
  author: 'Tom Coleman', 
  url: 'https://docs.meteor.com'
});
~~~
<%= caption "Browser console" %>

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<%= screenshot "4-4", "Adding posts via the console" %>

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<% note do %>

### Inspecting DOM Changes

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<% end %>

### Connecting Collections: Publications and Subscriptions

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~~~bash
$ meteor remove autopublish
~~~

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~~~js
Meteor.publish('posts', function() {
  return Posts.find();
});
~~~
<%= caption "server/publications.js" %>

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~~~js
Meteor.subscribe('posts');
~~~
<%= caption "client/main.js" %>

<%= commit "4-4", "Removed `autopublish` and set up a basic publication." %>

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### Conclusion

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