a simple twitter app with ruby on rails – messages with ajax

8/8/2019 A Simple Twitter App with Ruby on Rails Messages With Ajax

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A Simple Twitter App with Ruby on Rails Messages

With Ajax

Ruby on Rails is a web application framework that promotes rapid development.

Clients demands are ever increasing yet they still expect the same quality of output.

Frameworks, like Rails, help to achieve this; why? here are some of the reasons:

The second part of this tutorial: A Simple Twitter App with Ruby on Rails

User Authentication

The third part of this tutorial: A Simple Twitter App with Ruby on Rails

Building Friendships

Convention over Configuration (CoC):

This is used to reduce the amount of up-front configuartion. The idea is; if you

abide by certain coding conventions, you will have little, to none, configuration

to do.

Object-Relational Mapping (ORM):

ORM reducing coupling to the database. This abstraction allows you changed

the DBMS provider with little trouble.

Structured Code:

The MVC pattern forces you to organise your code in a clean, structured way.

This results in more maintainable code.

Plugins:

Plugins save you from re-inventing the wheel every time you want to add

functionality to your app. For instance, making you web app capable of

performing searches can be easily added with the acts_as_ferret plugin. There

are many more plugins!

Who is this Tutorial for?
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This tutorial is for people who have learnt the basics of Rails and want to take things to

the next level. This tutorial is not a beginners guide for getting started with Rails. If you

are just starting out with Rails I suggest this article from Six Revisions.

What this Tutorial Covers

In the first part of this three part series, we cover setting up a simple message model,

which will hold the messages posted. Further to this, we will learn how to post a

message asynchronously, using AJAX.

View Demo of Twitter App with Ruby on Rails

Basic Application Design

Ok, so youve decided to create a twitter style micro-blog using Ruby on Rails. First,

we need to think about our basic requirements and from this we can model our

application.

There are many ways that this can be done, but we will use a simple technique in which

you jot down a few paragraphs about how and what the application is expected to do

then highlight the nouns. So, lets try it.

My web app should work in a similar way to twitter. Users should be able to register

with the site and create shortposts. Users should be able to follow other users. Each

user should be able to see their own posts plus the users they are following.

Note that Ive been selective in what nouns Ive highlighted. You only really need to

take notice of the nouns which you feel will need to store data to the database.

I know there is more to twitter than this, but lets leave it simple. As you can see the

nouns, which will need to store data to the database are posts and users. So we

require two models:

In the first part of the tutorial, we are going to deal with posts only.

Post User

Creating the Project Files

Before we do anything we need to create a project for our twitter web app.

1. > rails twitter -d mysql

As you can see, I will be using MySQL as the DBMS, however, feel free to use

whatever database you want.
http://sixrevisions.com/web-development/how-to-create-a-blog-from-scratch-using-ruby-on-rails/http://www.therailworld.com/posts/18-Create-a-Twitter-App-with-Rails-Demo-Datahttp://sixrevisions.com/web-development/how-to-create-a-blog-from-scratch-using-ruby-on-rails/http://www.therailworld.com/posts/18-Create-a-Twitter-App-with-Rails-Demo-Data


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Open the database.yml file in the config folder and modify the password as required. An

example is shown below.

1. development:

2. adapter: mysql

3. encoding: utf84. database: twittest_development

5. pool: 5

6. username: root

7. password: yourpassword

8. host: localhost

Now, create the database with the rake command.

1. > rake db:create

Implementing the basic Message Model

So lets go right ahead and generate the Post model and migrate it.

1. > ruby script/generate model post message:text

2. > rake db:migrate

Controller

Now, lets create a controller for the post model.

1. > ruby script/generate controller posts

We need to set up some methods for interacting with the model. Edit your

posts_controller.rb file and add the following methods:

view plaincopy to clipboard print ?

1. class PostsController < ApplicationController

2. def index3. @posts = Post.all(:order => "created_at DESC")

4. respond_to do |format|

5. format.html

6. end

7. end

8.

9. def create

10. @post = Post.create(:message => params[:message])


12. if @post.save

13. format.html { redirect_to posts_path }14. else
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15. flash[:notice] = "Message failed to save."

16. format.html { redirect_to posts_path }

17. end

18. end

19. end

20. end

We only need two methods, index and create. The index method creates an instance

variable containing all the posts in descending order. The create method is used to

create a new post.

Views

Lets create the index view. First, well create a partial for posts. Create a file called

_post.html.erb in the views/posts folder and add the code below.

1.

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2.

The index view is now very simple. Create a file called index.html.erb in the

views/posts folder and add the code below.

1. @posts %>

Create some Posts

Open a console session and create a few new messages, as shown below.


1. > ruby script/console

2. Loading development environment (Rails 2.3.2)

3. >> Post.create!(:message => "My first post" )

4. >> Post.create!(:message => "Post number two!" )

Create a Form for Posts

Obviously youre not going to get the user to use the console to create messages. So,our next task is to inject some functionality into our web app to allow the user to create

messages. Twitter has an input box above the indexed messages, which is used for

submitting a new message; We will keep our web app the same.

First, we will create a partial for the form, then we will render that partial at the top of

the index view. Create a file called _message_form.html.erb in the posts view folder

and add the following code:


1. "posts", :action => "create") do %>

2.
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3. "44x6") %>

4.

5.

Now, we need to modify the index view to render this partial at the top. Open the

index.html.erb file and modify the code as follows:


1. "message_form" %>

2. @posts %>

For this to work we need to make one last modification. Open the route.rb file and map

a new posts resource, as shown below. (Note: the comments from this file have been

removed).


1. ActionController::Routing::Routes.draw do |map|

2. map.resources :posts

3. map.connect ':controller/:action/:id'

4. map.connect ':controller/:action/:id.:format'

5. end

This creates a few named routes. If you look back to the create method in the posts

controller, youll see that we make use of the posts_path named route; Defining the

posts resource makes this named route available.

So, lets fire up the web server and a see how things look.

1. > ruby script/server

Now open a browser and go to http://localhost:3000/posts. You should see a screen, as

shown below.


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Adding some AJAX

AJAX allows you to make asynchronous requests to the server using JavaScript. We

will make use of AJAX to make the posting a message a bit smoother.

When the user clicks on the Update button, we want the message to update withoutrefreshing the browser. We have a few things to do to add AJAX functionality. First,

lets change the create method in the posts controller:


1. def create

2. @post = Post.create(:message => params[:message])


4. if @post.save


6. format.js7. else

8. flash[:notice] = "Message failed to save."


10. end

11. end

12. end

The only change here is the format.js code, allowing the create method to respond to

JavaScript. Next, we need to create a posts layout file. In the views/layout folder create

a file called posts.html.erb and add the following code:



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1.

2.

3.

4.

5. 6.

7.

8.

9.

10.

11.

The main purpose of this is to make use of the javascript_include_tag call, which

includes the relevant JavaScript files for AJAX and some visual effects. Next, we need

to make a small addition to the index view (index.html.erb).


1. "message_form" %>

2.

3. @posts %>

4.

As you can see all we have added is a div block surrounding the posts partial. This will

be used later when we are specifying where the AJAX response should be placed.

Nearly there! Now we will add a div_for block to our post partial (_post.html.erb).


1.

2.

Posted ago

3.

4.

Edit the _message_form.html.erb partial and change the form_tag call to

form_remote_tag as show in the code extract below:


1. "posts", :action => "create") do %>

The div_for operation create a div block with a unique id, this is especially useful when

looping through several records. Finally, we need to create the rjs template. To do this,

create a file called create.js.rjs in the views/posts folder and add the following code.

1. page.insert_html :top, :posts, :partial => @post

2. page[@post].visual_effect :highlight
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The first line specifies that a new post partial will be rendered at the top of the posts div

when the asynchronous call responds. The second line specifies that a highlight visual

effect will be applied to that block when it is rendered.

Thats it! Start you web server again, browse to http://localhost:3000/posts and give it a

go.

Make it Look Pretty!

Ive created a stylesheet, which we can use to make things look a bit more respectful.

Create a file called layout.css in the public/stylesheets folder then add the following

CSS code:


1. body

2. {

3. font-family: tahoma, sans-serif;

4. font-size: 18px;

5. background-color: #4B7399;

6. width: 100%;

7. color: #ffffff;

8. margin: 0;

9. text-align: center;

10. }11.

12. #content

13. {

14. width: 800px;

15. margin: 0 auto;

16. text-align: left;

17. }

18.

19. .post

20. {

21. padding: 5px 20px 5px 20px;22. background-color: #ffffff;

23. margin: 20px 0 20px 0;

24. color: #000000;

25. }

Finally, you will need to add stylesheet_link_tag call to the posts.html.erb layout file.

As per below, the call should be placed in the head tag.


1. 2.


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3.

4.

OK! It doesnt look that pretty, but it will do for our purposes.

Setting up a Home Page

To have the root URL (http://localhost:3000) direct the user towards your posts you will

first need to delete the public/index.html file. Do this now.

The second thing you need to do is set up a route in your config\routes.rb file. Open

routes.rb in notepad and add a new line to the end using map.root, as shown below.


1. ActionController::Routing::Routes.draw do |map|

2. map.resources :posts

3. map.connect ':controller/:action/:id'

4. map.connect ':controller/:action/:id.:format'

5. map.root :controller => "posts"

6. end

For more on routes, try the Rails API Documentation

Now if you browse to http://localhost:3000. The request will be routed to the posts

controller.

Summary
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This concludes the first part of the series. Depending on the popularity of this article,

parts 2 and 3 will follow shortly.

a simple twitter app with ruby on rails – messages with ajax

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