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    assignment.rb associations.rb basics.rb callbacks.rb composite.rb conversions.rb database.rb index.rb modifiers.rb queries.rb spec.rb validations.rb

  • database.rb

  • ¶

    Multiple Collections and Databases in [Mongo Model][mongodb_model].

    By default models use default database, but You can use multiple databases and save model to any collection. create This is advanced topic, usually You don’t need these features, You can safely ignore this sample if You don’t need such features.

    In this example we’ll create Post model and save it to different databasescreate and collections.

    require 'mongo/model'
  • ¶

    Connecting to test database and cleaning it before starting.

    Mongo::Model.default_database_name = :default_test
Mongo::Model.default_database.clear
db = Mongo::Model.default_database
  • ¶

    Collections

  • ¶

    Defining Post.

    class Post
  inherit Mongo::Model
  collection :posts

  attr_accessor :text
end
  • ¶

    Creating post in default :posts collection.

    post = Post.new text: 'Zerg infestation found on Tarsonis!'
post.save
p db.posts.count                                 # => 1
  • ¶

    Creating post in custom collection

    post = Post.new text: 'Norad II crashed!'
post.save collection: db.drafts
p db.drafts.count                                # => 1
  • ¶

    Databases

  • ¶

    Let’s create model for Article and save it in another database. By default model use Mongo::Model.default_database, but we can use customcreate database and collection.

    class Article < Post
  db :default_test2
  collection :articles
end
  • ¶

    Now our Article uses :default_test2 database.

    p Article.db.name                                # => "default_test2"
  • ¶

    But in real life scenario it’s not very convinient to use real database name in models, usually it’s more convinient to use aliases and specify realcreate names in config. create We can do this by owerriding Mongo.db method.

  • ¶

    Here’s our config, it map :db2 alias to the :default_test2 real name.

    DB_CONFIG = {db2: :default_test2}
  • ¶

    Overriding Mongo.db method and making it use our DB_CONFIG.

    module Mongo
  class << self
    alias_method :db_without_config, :db
    def db name
      name = DB_CONFIG[name] || name
      db_without_config name
    end
  end
end
  • ¶

    Now we can use database alias in our models.

    class Article
  db :db2
end
  • ¶

    The :db2 alias mapped to the :default_test2 name.

    p Article.db.name                                # => "default_test2"
  • ¶

    In this example we covered how to use multiple collections and databases.