# ActiveRecordSchema

*ActiveRecordSchema* is an ActiveRecord extension that allows you to write the database schema for a model within the model itself and to generate migrations directly from models.

Unlike other libraries (eg. mini_record) ActiveRecordSchema is not an alternative to Rails migrations, but rather a tool to simplify their use.

Install

    gem 'active_record_schema'
    
Update your bundle
  
    bundle install

## Usage

Create a model
    
    class Post < ActiveRecord::Base
        field :title
        field :body, :as => :text
        belongs_to :author, :class_name => "User"
    end

Run a migration generator each time you want to commit changes to database

    rails g migration init_posts_schema --from Post
  
Will generate the following migration

    class InitPostsSchema < ActiveRecord::Migration
      def change
        add_column :posts, :title, :string
        add_column :posts, :body, :text

        add_column :author_id, :integer
        index :author_id
      end
    end

Now you can migrate the database.

Later in the life cycle of the project... add a new field to `Post`
    
    class Post < ActiveRecord::Base
        field :title
        field :body, :as => :text
        belongs_to :author, :class_name => "User"
        field :pubdate, :as => :datetime
    end

Generate easily a new migration for the change:

    rails g migration add_pubdate_to_posts --from Post

Will generate:

    class AddPubdateToPosts < ActiveRecord::Migration
      def change
        add_column :posts, :pubdate, :datetime
      end
    end


## Has and Belongs To Many (HBTM) associations

Lets try to add a HBTM association to our `Post` model

_ex._

    # content.rb
    class Post < ActiveRecord::Base
      field :title
      field :body, :as => :text
      belongs_to :author, :class_name => "User"
      field :pubdate, :as => :datetime

      has_and_belongs_to_many :voters, :class_name => "User"
    end


Now running

    rails g migration add_voters_to_posts --from Post

Will generate:

    class AddVotersToPosts < ActiveRecord::Migration
      def change
        create_table :contents_users, :id => false do |t|
          t.integer  "content_id"
          t.integer  "user_id"
        end
        add_index :contents_users, "content_id"
        add_index :contents_users, "user_id"
      end
    end

## Single Table Inheritance (STI)

Call `#inheritable` inside the base class of your hierarchy to add the `type` column required by Single Table Inheritance.

_ex._

    # content.rb
    class Content < ActiveRecord::Base
      inheritable
  
      field :title
  
      has_and_belongs_to_many :voters, :class_name => "User"
      belongs_to              :author, :class_name => "User"
    
      timestamps
    end
    
  
    # article.rb
    class Article < Content
      field :body, :as => :text
    end
    
  
    # video.rb
    class Video < Content
      field :url
    end

run
    
    rails g migration init_contents --from Content

same as

    rails g migration init_contents --from Article
    
same as

    rails g migration init_contents --from Video
    
Will generate the following migration 

    class InitContents < ActiveRecord::Migration
      def change
        add_column :contents, :type, :string
        add_column :contents, :title, :string
        add_column :contents, :author_id, :string
        add_column :contents, :body, :text
        add_column :contents, :url, :string

        add_index :contents, :author_id

        create_table :contents_users, :id => false do |t|
          t.integer  "content_id"
          t.integer  "user_id"
        end
        add_index :contents_users, "content_id"
        add_index :contents_users, "user_id"
      end  
    end



## Contributing to active_record_schema
 
* Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet.
* Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it.
* Fork the project.
* Start a feature/bugfix branch.
* Commit and push until you are happy with your contribution.
* Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
* Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.


---

Copyright (c) 2012 mcasimir

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