Creating Simple Blogging Platform--Model

Creating Simple Blogging Platform--Model

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This tutorial assumes you have already completed:

  1. Install Ruby on Rails
  2. Create a Ruby on Rails application
  3. Create Static Pages - without this deploy will not work
  4. Install Git
  5. Create a remote Git Repository - optional but recommended
  6. Deploy application to Heroku
  7. Manage users with Devise
  8. How to add Twitter Bootstrap to a Ruby on Rails application - Advised

Let's make our website do something useful. How about building a blogging platform where users can share their stories. Our new web application will have the following features:

  • All users can create, edit, and delete own posts
  • All users can read other users posts

Step 1: Create "Post" model in Terminal

We are going to start by creating a new model for our posts. Open your terminal, navigate to your application. Make sure you type Post in a singular form with a capital letter. It's a rails convention.

bash


cd documents/projects/demo
$ rails generate model Post title:string body:text



invoke  active_record
create    db/migrate/20140507054439_create_posts.rb
create    app/models/post.rb
invoke    test_unit
create      test/models/post_test.rb
create      test/fixtures/posts.yml

Step 2: Open Migration File

Same as when we were generating model with Devise for our users, we generated some files: migration, model and test files. Let's open migration first.

db/migrate/20140507054439_create_posts.rb


class CreatePosts < ActiveRecord::Migration
  def change
    create_table :posts do |t|
      t.string :title
      t.text :body

      t.timestamps
    end
  end
end

This migration file will be used to create a new table in our database to hold posts. Think about it as a spreadsheet that will have rows and columns. Each row will contain information about one post; each column will contain a different type of information about our post. Our posts will have a title which will accept data type of string (not too long set of characters, like a sentence in any language), body that will accept data type "text" (possibly very long chunk of text). Rails will also create two columns created_at and updated_at with the line t.timestamps.

      id  |  title  |  body  |  created_at  |  updated_at
    -------------------------------------------------------
          |         |        |              |

Before we migrate the database, we can still make the changes to this file. We can add, rename and remove fields. After we migrate the database - we can NOT. In order to change the database after the migration we need to create new migration file, otherwise we're just asking for trouble.

Step 3: Open Post Model File

Second file is the actual post model:

app/models/post.rb


class Post < ActiveRecord::Base
end

At the moment we only have opening and closing lines with no custom code in between. Soon, we will come back to this file.

Step 4: Run Migrate

For now, let's migrate the database. In terminal window:

 

bash


$ rake db:migrate

== 20140507054439 CreatePosts: migrating ======================================
-- create_table(:posts)
   -> 0.0054s
== 20140507054439 CreatePosts: migrated (0.0055s) =============================

Now, our application has the ability to create posts and store them in the database. To see how it works, since we don't have any user interface yet, we will interact with the application through the console. Open a new terminal window, navigate to your application and run this command:

bash


$ rails console

Loading development environment (Rails 4.1.0)
2.1.1 :001 >

">" indicates that we are running Rails console. If you try typing bash commands here - they will fail. To exit console, either type "exit" or press "control + d" on your keyboard.

Step 5: Create a Post

Let's run some code in the command line:

bash


2.1.1 :001 > post = Post.new(title: "The first post ever", body: "Lorem ipsum dolor sit amet")

 => #<Post id: nil, title: "The first post ever", body: "Lorem ipsum dolor sit amet", created_at: nil, updated_at: nil>

We have just created a new variable "post", and assigned to it with "=" new instance of the Post. Post.new() - creates a new object in the memory. We can pass the parameters inside the parentheses, that will be used to assemble a new record. Notice that "title" and "body" match the names of the fields we have created when creating the model.

Step 6: Save Post

Also, you can see that the newly created model doesn't have an ID. When we ask for post.id, we get "nil" value. In our database, each record will always have an ID - it automatically creates a unique ID. Right now, record has an empty ID because it hasn't been saved yet. Method "new" only creates record in the memory and doesn't try to save it, therefore ID is not assigned.


2.1.1 :002 > post.id

=> nil

Let's save it:


2.1.1 :003 > post.save

(0.3ms)  begin transaction
SQL (0.5ms)  INSERT INTO "posts" ("body", "created_at", "title", "updated_at") VALUES (?, ?, ?, ?)  [["body", "Lorem ipsum dolor sit amet"], ["created_at", "2014-05-07 06:44:22.227792"], ["title", "The first post ever"], ["updated_at", "2014-05-07 06:44:22.227792"]]
(0.7ms)  commit transaction
=> true

Step 7: Check ID

Now, check if the ID is now assigned:


2.1.1 :004 > post.id
 => 1

Step 8: Create a new Post

Let's create one more post:


2.1.1 :005 > new_post = Post.new(title: "Second post", body: "Lorem Ipsum Dolor Sit Amet")
2.1.1 :005 > new_post.save



2.1.1 :005 > Post.count
 => 2

So we have a couple of records in the database already. Let's build a user interface to display those posts.

If you login you will be able to mark this tutorial as finished to track your progress



Comments

  • On: Frank wrote:

    Done! Syntax matters here. Thanks for the help.

  • On: Frank wrote:

    Solid, thanks! Syntax matters here, I had some trial and error.

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