Dynamic (prefixed at runtime) collection names for mongoid models

mongoid_prefixable.rb

# uber-hacky dynamic collection names for MongoID models:
# 
# class MyModel
#  include Mongoid::PrefixableDocument # ...instead of Mongoid::Document
#  include Mongoid::Timestamps
#
#  field :foobar, :type => Integer
#
#  def my_method; 123; end
#
#  freeze_stack! # this needs to be the last line in your model!
#
# end
#
# m = MyModel.new
#   => #<MyModelWrap _prefix: none, _id: 12312312, _type: nil >
# m.collection_name
#   => "my_model"
#
# m = MyModel.prefix("foobar").new
#   => #<FoobarMyModelWrap _prefix: foobar, _id: 12312312, _type: nil >
# m.collection_name
#   => "foobar_my_model"
#
# ~paul (paul@paulasmuth.com)

module Mongoid

  module PrefixableDocument
    def self.included(base) 
      base.class_eval do

        @@wrapped_stack = []
        @@wrapped_class = base
        
        def self.prefix(_prefix=nil)          
          @@wrapped_class.clone.tap do |wrapper_klass|
            wrapper_klass.class_eval do              

              @@wrapped_prefix = _prefix

              include Mongoid::Document
             
              def self.inspect
                "#<#{@@wrapped_class.name} _prefix: #{@@wrapped_prefix||'none'}>" 
              end

              def prefixed_inspect(inspection)
                "#<#{@@wrapped_class.name} _prefix: #{@@wrapped_prefix||'none'}, _id: #{id}, #{inspection * ', '}>" 
              end

            end
                   
            wrapper_klass.store_in([_prefix,@@wrapped_class.name.pluralize.downcase].compact.join("_"))
            
            @@wrapped_stack.each{ |m,a| wrapper_klass.send(m,*a) }

          end          
        end

        def self.method_missing(_method, *args)      
          if @@wrapped_stack.frozen?
            self.prefix.send(_method, *args)
          else 
            @@wrapped_stack << [_method, args]
          end          
        end

        def self.freeze_stack!
          @@wrapped_stack.freeze
        end

      end
    end
  end

  module Inspection

      def inspect        
        inspection = []
        inspection.concat(inspect_fields).concat(inspect_dynamic_fields)
        return prefixed_inspect(inspection) if respond_to?(:prefixed_inspect)          
        "#<#{self.class.name} _id: #{id}, #{inspection * ', '}>"        
      end

  end

end

Hey, have you tried to utylize this extension while running pararel specs?

Works nicely, thanks!

Just a note, with MongoId 4.0.0 store_in has changed slightly, so line 54 needs to be

wrapper_klass.store_in(collection: [_prefix,@@wrapped_class.name.pluralize.downcase].compact.join("_"))

I inherited some code that used this gist. Word to the wise, don't use this with more than one class! Direct assignment of class variables in a mixins will have bad results. Replace the assignments:

      @@wrapped_stack = []
      @@wrapped_class = base

with

      base.send :class_variable_set, :@@wrapped_stack, []
      base.send :class_variable_set, :@@wrapped_class, base

Similarly, use :class_variable_get instead of direct reference of any @@ variable.
https://gist.github.com/jygeer/4492c261916d8d3a384f