12-pagination.md.erb

---
title: Pagination
slug: pagination
date: 0012/01/01
number: 12
contents: Learn more about Meteor's subscriptions, and how we can use them to control data.|Implement infinite-style pagination.|Use the `iron-router-progress` package to implement a nifty iOS-style progress bar.|Create a special subscription to deal with direct links to posts page.
paragraphs: 67
---


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### Adding More Posts

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~~~js
// Fixture data 
if (Posts.find().count() === 0) {

  //...
  
  Posts.insert({
    title: 'The Meteor Book',
    userId: tom._id,
    author: tom.profile.name,
    url: 'http://themeteorbook.com',
    submitted: new Date(now - 12 * 3600 * 1000),
    commentsCount: 0
  });
  
  for (var i = 0; i < 10; i++) {
    Posts.insert({
      title: 'Test post #' + i,
      author: sacha.profile.name,
      userId: sacha._id,
      url: 'http://google.com/?q=test-' + i,
      submitted: new Date(now - i * 3600 * 1000),
      commentsCount: 0
    });
  }
}
~~~
<%= caption "server/fixtures.js" %>
<%= highlight "15~24" %>

////

<%= screenshot "12-1", "Displaying dummy data. " %>

<%= commit "12-1", "Added enough posts that pagination is necessary." %>

### Infinite Pagination

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~~~js
Router.configure({
  layoutTemplate: 'layout',
  loadingTemplate: 'loading',
  notFoundTemplate: 'notFound',
  waitOn: function() { 
    return [Meteor.subscribe('notifications')]
  }
});
~~~
<%= caption "lib/router.js" %>
<%= highlight "6" %>

////

~~~js
//...

Router.route('/:postsLimit?', {
  name: 'postsList',
});

//...
~~~
<%= caption "lib/router.js" %>
<%= highlight "3" %>

////

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////

~~~js
//...

Router.route('/:postsLimit?', {
  name: 'postsList',
  waitOn: function() {
    var limit = parseInt(this.params.postsLimit) || 5; 
    return Meteor.subscribe('posts', {sort: {submitted: -1}, limit: limit});
  }
});

//...
~~~
<%= caption "lib/router.js" %>
<%= highlight "5~8" %>

////

~~~js
Meteor.publish('posts', function(options) {
  check(options, {
    sort: Object,
    limit: Number
  });
  return Posts.find({}, options);
});

Meteor.publish('comments', function(postId) {
  check(postId, String);
  return Comments.find({postId: postId});
});

Meteor.publish('notifications', function() {
  return Notifications.find({userId: this.userId});
});
~~~
<%= caption "server/publications.js" %>
<%= highlight "1~7" %>

<% note do %>

### Passing Parameters

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~~~js
Meteor.publish('posts', function(sort, limit) {
  return Posts.find({}, {sort: sort, limit: limit});
});
~~~

<% end %>

////

////

~~~js
//...

Router.route('/:postsLimit?', {
  name: 'postsList',
  waitOn: function() {
    var limit = parseInt(this.params.postsLimit) || 5; 
    return Meteor.subscribe('posts', {sort: {submitted: -1}, limit: limit});
  },
  data: function() {
    var limit = parseInt(this.params.postsLimit) || 5; 
    return {
      posts: Posts.find({}, {sort: {submitted: -1}, limit: limit})
    };
  }
});

//...
~~~
<%= caption "lib/router.js" %>
<%= highlight "9~14" %>

////

////

////

~~~js
Router.configure({
  layoutTemplate: 'layout',
  loadingTemplate: 'loading',
  notFoundTemplate: 'notFound',
  waitOn: function() { 
    return [Meteor.subscribe('notifications')]
  }
});

Router.route('/posts/:_id', {
  name: 'postPage',
  waitOn: function() {
    return Meteor.subscribe('comments', this.params._id);
  },
  data: function() { return Posts.findOne(this.params._id); }
});

Router.route('/posts/:_id/edit', {
  name: 'postEdit',
  data: function() { return Posts.findOne(this.params._id); }
});

Router.route('/submit', {name: 'postSubmit'});

Router.route('/:postsLimit?', {
  name: 'postsList',
  waitOn: function() {
    var limit = parseInt(this.params.postsLimit) || 5; 
    return Meteor.subscribe('posts', {sort: {submitted: -1}, limit: limit});
  },
  data: function() {
    var limit = parseInt(this.params.postsLimit) || 5; 
    return {
      posts: Posts.find({}, {sort: {submitted: -1}, limit: limit})
    };
  }
});

var requireLogin = function() {
  if (! Meteor.user()) {
    if (Meteor.loggingIn()) {
      this.render(this.loadingTemplate);
    } else {
      this.render('accessDenied');
    }
  } else {
    this.next();
  }
}

Router.onBeforeAction('dataNotFound', {only: 'postPage'});
Router.onBeforeAction(requireLogin, {only: 'postSubmit'});
~~~
<%= caption "lib/router.js" %>
<%= highlight "6,25~37" %>

<%= commit "12-2", "Augmented the postsList route to take a limit." %>

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<%= screenshot "12-2", "Controlling the number of posts on the homepage. " %>

<% note do %>

### Why Not Pages?

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<% end %>

### Creating a Route Controller

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~~~js
//...

PostsListController = RouteController.extend({
  template: 'postsList',
  increment: 5, 
  postsLimit: function() { 
    return parseInt(this.params.postsLimit) || this.increment; 
  },
  findOptions: function() {
    return {sort: {submitted: -1}, limit: this.postsLimit()};
  },
  waitOn: function() {
    return Meteor.subscribe('posts', this.findOptions());
  },
  data: function() {
    return {posts: Posts.find({}, this.findOptions())};
  }
});

//...

Router.route('/:postsLimit?', {
  name: 'postsList'
});

//...
~~~
<%= caption "lib/router.js" %>
<%= highlight "3~18, 25" %>

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<%= commit "12-3", "Refactored postsLists route into a RouteController." %>

### Adding A Load More Link

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~~~js
//...

PostsListController = RouteController.extend({
  template: 'postsList',
  increment: 5, 
  postsLimit: function() { 
    return parseInt(this.params.postsLimit) || this.increment; 
  },
  findOptions: function() {
    return {sort: {submitted: -1}, limit: this.postsLimit()};
  },
  waitOn: function() {
    return Meteor.subscribe('posts', this.findOptions());
  },
  posts: function() {
    return Posts.find({}, this.findOptions());
  },
  data: function() {
    var hasMore = this.posts().count() === this.postsLimit();
    var nextPath = this.route.path({postsLimit: this.postsLimit() + this.increment});
    return {
      posts: this.posts(),
      nextPath: hasMore ? nextPath : null
    };
  }
});

//...
~~~
<%= caption "lib/router.js" %>
<%= highlight "15~25" %>

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~~~html
<template name="postsList">
  <div class="posts">
    {{#each posts}}
      {{> postItem}}
    {{/each}}
    
    {{#if nextPath}}
      <a class="load-more" href="{{nextPath}}">Load more</a>
    {{/if}}
  </div>
</template>
~~~
<%= caption "client/templates/posts/posts_list.html" %>
<%= highlight "7~10" %>

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<%= screenshot "12-3", "The “load more” button. " %>

<%= commit "12-4", "Added nextPath() to the controller and use it to step through posts." %>

### A Better User Experience

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~~~js
//...

PostsListController = RouteController.extend({
  template: 'postsList',
  increment: 5, 
  postsLimit: function() { 
    return parseInt(this.params.postsLimit) || this.increment; 
  },
  findOptions: function() {
    return {sort: {submitted: -1}, limit: this.postsLimit()};
  },
  subscriptions: function() {
    this.postsSub = Meteor.subscribe('posts', this.findOptions());
  },
  posts: function() {
    return Posts.find({}, this.findOptions());
  },
  data: function() {
    var hasMore = this.posts().count() === this.postsLimit();
    var nextPath = this.route.path({postsLimit: this.postsLimit() + this.increment});
    return {
      posts: this.posts(),
      ready: this.postsSub.ready,
      nextPath: hasMore ? nextPath : null
    };
  }
});

//...
~~~
<%= caption "lib/router.js" %>
<%= highlight "12~14, 23" %>

////

~~~html
<template name="postsList">
  <div class="posts">
    {{#each posts}}
      {{> postItem}}
    {{/each}}
    
    {{#if nextPath}}
      <a class="load-more" href="{{nextPath}}">Load more</a>
    {{else}}
      {{#unless ready}}
        {{> spinner}}
      {{/unless}}
    {{/if}}
  </div>
</template>
~~~
<%= caption "client/templates/posts/posts_list.html" %>
<%= highlight "10~12" %>

<%= commit "12-5", "Add a spinner to make pagination nicer." %>

### Accessing Any Post

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<%= screenshot "12-4", "An empty template." %>

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~~~js
Meteor.publish('posts', function(options) {
  return Posts.find({}, options);
});

Meteor.publish('singlePost', function(id) {
  check(id, String)
  return Posts.find(id);
});

//...
~~~
<%= caption "server/publications.js" %>
<%= highlight "5~7" %>

////

~~~js
//...

Router.route('/posts/:_id', {
  name: 'postPage',
  waitOn: function() {
    return [
      Meteor.subscribe('singlePost', this.params._id),
      Meteor.subscribe('comments', this.params._id)
    ];
  },
  data: function() { return Posts.findOne(this.params._id); }
});

Router.route('/posts/:_id/edit', {
  name: 'postEdit',
  waitOn: function() { 
    return Meteor.subscribe('singlePost', this.params._id);
  },
  data: function() { return Posts.findOne(this.params._id); }
});

//...
~~~
<%= caption "lib/router.js" %>
<%= highlight "6~9,16~18" %>

<%= commit "12-6","Use a single post subscription to ensure that we can always see the right post." %>

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