Mongoid with Rails 3

Hi, Every one , I feel that my posts are useful for you to get knowledge on Rails and please suggest me if you have any useful topics so that we will discuss more on those topics . here I am going to explain how Mongoid works with rails3 , here I explained some basics to get start with mongoid .
    as i have posted previously mongodb is so flexible and its document oreiented . We have sevaral ORM 's in the market we all know that ActiveRecord is one of the famous ORM for rails when we are dealing with relational databases . Now here we are dealing with ODM 's means Object Document Mapper . There are several ODM ' s are there few things i listed out here in conjuction with rails

  1.MongoMapper  
  2.Mongoid  
  3.Mongomatic  
  4.MongoODM  
  5.MongoModel  
  6.DriverAPILayer  

these are all ruby based ODM's Here i am going to create small application which will give some idea about how to use Mongoid

Step 1:

  install the mongoid gem by typing the following at your terminal  
   "gem install mongoid " or else you can add it your gem file  

Step2 : create a new rails application

 rails new mongoid_app  

Step3 : go to your mongoid_app

 cd monoid_app  

Step 4 : here I want to create two models Movie and Dancer and later i will associate both .
    First generate scaffold for movie model

 rails g scaffold Movie name:string   

which will create model , controller and veiws for movie model , in the same way create dancer model also

 rails g Dancer name:string  

then open your model and simply just include the following line in your model

 include Mongoid::Document  

follow the example below Ex :

 class Movie  
  include Mongoid::Document  
  field :name , type:String  
 end  

this will give ability to our class to act as a mongo document . Here we can see that our movie model contains only one field called name , if we want to add extra fields then no need of migrations here ,(oh sounds cool) simply add field name and type , once you enter the data and run the application it will add to database really how simple it is ! I will add one more field here

 class Movie  
  include Mongoid::Document  
  field :name , type:String  
  field :budget , type : Integer  
 end  

in the same way include Mongoid::Document to the Dancer model also .

 class Dancer  
  include Mongoid::Document  
  field :name , type:String  
 end  

now i will associate both models with has_many relation , just like the activerrecord relations we can add here also here I am going to establish Movie has_many dacers . See the following code snippet

 class Movie  
  include Mongoid::Document  
  field :name , type:String  
  field :budget , type : Integer  
 embeds_many :dancers  
 end  

and Dancer model is

 class Dancer  
  include Mongoid::Document  
  field :name , type:String  
  embedded_in :artist  
 end  

now we can query model simply by the following

 fetch Movie Model :  
  @movie = Movie.first  
 fetch movie related dancers  
  @dancers = @movie.dancers  

I hope this will help you to give some idea mongoid with rails .I welcome your comments on this article so that i can improve further .thank you Thanks Ratnakar V

About the Author

Ratnakar is a Software Engineer, Blogger from India.His articles mainly focus on Ruby on Rails Technology.

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