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conversions.rb

Conversions for Mongo Model.

In this example we’ll create simpel Blog and discover how to convert models to JSON, filter attributes, and define conversion profiles for Composite Model.

 
require 'mongo/model'

Connecting to test database and cleaning it before starting.

 
Mongo::Model.default_database_name = :default_test
Mongo::Model.default_database.clear

Defining Post with Comments.

 
class Post
  inherit Mongo::Model
  collection :posts

  attr_accessor :text, :token

  def comments; @comments ||= [] end
end

class Comment
  inherit Mongo::Model

  attr_accessor :text, :token
end

Creating post and converting it to JSON:

{
  text:     ‘Zergs found!’,
  token:    10
  comments: [
    {
      text:  ‘Where?’,
      token: 11
    },
    {
      text:  ‘On Tarsonis.’,
      token: 12
    }
  ]
}

post = Post.new text: 'Zergs found!', token: 10
post.comments << Comment.new(text: 'Where?', token: 11)
post.comments << Comment.new(text: 'On Tarsonis.', token: 12)
puts post.to_json

We can filter attributes using :only, :except, :methods options.

{
  text: ‘Zergs found!’
}

puts post.to_json(only: :text)

Profiles

You can use filter options to control what attributes will be converted to JSON, but this filters won’t allow You to specify attributes on embedded models. To do so You need to use conversion profiles.

 

      		
    

    

      
        

          
        

        
Those tokens on post and comments are secret and we don’t want to expose it
to public. We need to define profile that will filter these secret tokens.

      		
      
        
class Post
  profile :public, except: :token
end
class Comment
  profile :public, except: :token
end

      		
    

    

      
        

          
        

        
Now we can use public profile in conversion and filter token attributes:



{
  text:     ‘Zergs found!’,
  comments: [
    {
      text:  ‘Where?’
    },
    {
      text:  ‘On Tarsonis.’
    }
  ]
}


      		
      
        
puts post.to_json(profile: :public)

      		
    

    

      
        

          
        

        
In this example we covered conversions, attribute filtering and
conversion profiles.