Question

How to change the current MongoMapper database at runtime?

Also, is there a way of mapping a model to a database whose name is dynamically calculated? For instance:

class MyEntity
    include MongoMapper::Document
    set_database_name "#{some_dynamic_value}"
end

Answer 1

If you want to use a specific database for a model, do…

class MyEntity
  include MongoMapper::Document
  set_database_name "entities_database_development"
end

You can do do string interpolation there, but that’s only resolved when the class is loaded and then never again.

To calculate a database name every single time a database is needed, override either the class or instance database method.

class MyEntity
  include MongoMapper::Document
  def database
    connection.db("my_database_#{rand}_development")
  end
end

See the persistence plugin source to get an idea of the kind of damage you can do by overriding.